Insulating film and semiconductor device including the same

ABSTRACT

It is made possible to provide an insulating film that can reduce the leakage current. An insulating film includes: an amorphous oxide dielectric film containing a metal, hydrogen, and nitrogen. The nitrogen amount [N] and the hydrogen amount [H] in the oxide dielectric film satisfy the following relationship: {[N]−[H]}/2≦1.0×10 21  cm −3 .

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2008-20774 filed on Jan. 31, 2008in Japan, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Described herein is an insulating film of a metal oxide containinghydrogen and a metal, and a semiconductor device including theinsulating film.

2. Related Art

To secure the charge to be induced at the channel of a MISFET (metalinsulator semiconductor field effect transistor), the gate insulatingfilm is normally made thinner, and the capacity is made largeraccordingly. As a result, the SiO₂ film as the gate insulating film hasbecome thinner, and at the present, it is now as thin as 1 nm or less.However, there is a large gate leakage current in the SiO₂ film, and thepower consumption cannot be restricted to an allowable amount due towasting of standby energy. For example, a 0.8-nm thick SiO₂ film has agate leakage current as large as 1 kA/cm², and the large powerconsumption presents a serious problem.

To reduce the power consumption, it is effective to increase the filmthickness. Therefore, the use of an insulating film made of a high-kmaterial that can maintain a sufficient charge amount even if the filmthickness of the insulating film becomes thicker than that of the SiO₂film is being considered. Various kinds of metal oxides have been knownas stable high-k materials. The most promising materials for theinsulating films having such characteristics include HfO₂, ZrO₂,silicates of those materials (HfSiO and ZrSiO), aluminates of thosematerials (HfAlO, ZrAlO), and LaAlO₃.

However, a high-k metal oxide tends to contain oxygen defects, as willbe described later. Therefore, large current leakage often occurs due tothe oxygen defects, and the reliability becomes poorer.

High-k oxynitrides (HfON, ZrON, HfSiON, and ZrSiON) are also expected tobe used for the gate insulating film. However, with a small amount ofnitrogen, crystallization occurs in the insulating film, and theinsulation characteristics are degraded. Therefore, it is necessary toadd a large amount of nitrogen. When a large amount of nitrogen isadded, however, as described hereinbelow, more oxygen defects are causeddue to the introduction of nitrogen, and large current leakage occurs.As a result, the reliability becomes poorer. If nitrogen exists in thevicinity of the interface between the substrate and the insulating film,fixed charges are generated, and the interfacial structure is disturbed.Therefore, it is preferable to form a structure in which nitrogen islocated at a distance from the interface between the substrate and theinsulating film (JP-A 2005-353999 (KOKAI)).

As described above, in a case where a high-k oxide or oxynitride is usedfor the insulating film, oxygen defects are easily formed, and largecurrent leakage occurs due to the oxygen defects. As a result, thereliability becomes poorer.

SUMMARY OF THE INVENTION

The present invention has been made in view of these circumstances, andan object thereof is to provide an insulating film that can reduce theleakage current, and a semiconductor device having the insulating film.

An insulating film according to a first aspect of the present inventionincludes: an amorphous oxide dielectric film containing a metal,hydrogen, and nitrogen, the nitrogen amount [N] and the hydrogen amount[H] in the oxide dielectric film satisfying the following relationship:

{[N]−[H]}/2≦1.0×10²¹ cm⁻³.

An insulating film according to a second aspect of the present inventionincludes: an amorphous oxide dielectric film containing a quadrivalentmetal, a trivalent metal, and hydrogen, the trivalent metal amount [IIImetal] and the hydrogen amount [H] in the oxide dielectric filmsatisfying the following relationship: {[III metal]−[H]}/2≦1.0×10²¹cm⁻³.

An insulating film according to a third aspect of the present inventionincludes: an amorphous oxide dielectric film containing a quadrivalentmetal, a divalent metal, and hydrogen, the divalent metal amount [IImetal] and the hydrogen amount [H] in the oxide dielectric filmsatisfying the following relationship: {2×[II metal]−[H]}/2≦1.0×10²¹cm⁻³.

An insulating film according to a fourth aspect of the present inventionincludes: an amorphous oxide dielectric film containing a trivalentmetal, a divalent metal, and hydrogen, the divalent metal amount [IImetal] and the hydrogen amount [H] in the oxide dielectric filmsatisfying the following relationship: {[II metal]−[H]}/2≦1.0×10²¹ cm⁻³.

A semiconductor device according to a fifth aspect of the presentinvention includes: a semiconductor substrate; a source region and adrain region provided at a distance from each other in the semiconductorsubstrate; the insulating film according to the first aspect, providedon a portion of the semiconductor substrate, the portion being a channelregion between the source region and the drain region; and a gateelectrode provided on the insulating film.

A semiconductor device according to a sixth aspect of the presentinvention includes: a first electrode; the insulating film according tothe first aspect, provided on the first electrode; and a secondelectrode provided on the insulating film.

A semiconductor device according to a seventh aspect of the presentinvention includes: a semiconductor substrate; a source region and adrain region provided at a distance from each other in the semiconductorsubstrate; a first insulating film provided on a portion of thesemiconductor substrate, the portion being a channel region between thesource region and the drain region; a first electrode provided on thefirst insulating film; a second insulating film provided on the firstelectrode; and a second electrode provided on the second insulatingfilm, at least one of the first insulating film and the secondinsulating film being the insulating film according to the first aspect.

A semiconductor device according to an eighth aspect of the presentinvention includes: a semiconductor substrate; a source region and adrain region provided at a distance from each other in the semiconductorsubstrate; a first insulating film provided on a portion of thesemiconductor substrate, the portion being a channel region between thesource region and the drain region; a charge trapping film provided onthe first insulating film; a second insulating film provided on thecharge trapping film; and an electrode provided on the second insulatingfilm, at least one of the first insulating film, the charge trappingfilm, and the second insulating film being the insulating film accordingto the first aspect.

According to a ninth aspect of the invention, there is provided asemiconductor device including: a first metal; oxygen; hydrogen; and amaterial being one of nitrogen and a second metal different from thefirst metal, wherein amount of the hydrogen is expressed as [H], amountof the material is expressed as [X], and a valence number differencebetween the first metal and the second metal or between oxygen andnitrogen is expressed as k, a following relationship:

{k×[X]−[H]}/2≦1.0×10²¹ cm⁻³

is satisfied, and

if the material is the second metal, the first metal is a quadrivalentmetal element, and the second metal is a trivalent metal element, amountof which is expressed as [trivalent element], then [X]=[trivalentelement] and k=1,

if the material is the second metal, the first metal is a quadrivalentmetal element, and the second metal is a divalent metal element, amountof which is expressed as [divalent element], then [X]=[divalent element]and k=2,

if the material is the second metal, the first metal is a trivalentmetal element, and the second metal is a divalent metal element, amountof which is expressed as [divalent element], then [X]=[divalent element]and k=1, and

if the material is nitrogen, amount of which is expressed as [N], then[X]=[N] and k=1.

In the ninth aspect, it is preferable that a following relationship issatisfied

{k×[X]−[H]}/2≦3.0×10²⁰ cm⁻³.

In the ninth aspect, it is preferable that following relationships aresatisfied

6.4×10¹⁹ cm⁻³≦[X]≦1.6×10²² cm⁻³/k ; and

6.4×10¹⁹ cm⁻³≦[H]≦1.6×10²² cm⁻³.

In the ninth aspect, it is preferable that following relationships aresatisfied

3.0×10²⁰ cm⁻³≦[X]≦2.0×10²¹ cm⁻³/k; and

3.0×10²⁰ cm⁻³≦[H]≦2.0×10²¹ cm⁻³.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the relationship between the amount of nitrogen [N] to beadded to a high-dielectric film and the band offset (ΔE) with respect toa silicon substrate;

FIGS. 2( a) to 2(c) illustrate the effect achieved when nitrogen N isadded to a high-dielectric film, the effect achieved when hydrogen H isadded, and the effect achieved when both are added;

FIG. 3 illustrates the regular lattice structure of HfO₂;

FIGS. 4( a) to 4(d) illustrate the process in which oxygen defectsdisappear in an insulating film of an embodiment;

FIG. 5 illustrates a lattice structure to be a NVoN structure that isformed by introducing nitrogen N into HfO₂ and has oxygen defects Vo;

FIG. 6 illustrates a lattice structure to be a (NVo+N) structure that isformed by introducing nitrogen N into HfO₂ and has oxygen defects Vo;

FIG. 7 illustrates a lattice structure that has N—H pairs introducedinto HfO₂;

FIGS. 8A and 8B are cross-sectional views illustrating a method forforming an insulating film in accordance with an embodiment;

FIG. 9 is a graph showing a rapid change of the band offset observedwhen {[N]−[H]}/2 is 7.4 to 8.33 atomic % in an embodiment;

FIG. 10 is a graph showing the results of SIMS analysis made on aninsulating film in accordance with an embodiment;

FIGS. 11A and 11B are cross-sectional views illustrating a method formanufacturing a MISFET having a damascene gate structure;

FIGS. 12( a) to 12(c) illustrate the effect achieved when aluminum Al isadded to a high-dielectric film, the effect achieved when hydrogen H isadded, and the effect achieved both are added;

FIG. 13 shows a lattice structure that has pairs of Al (a trivalentmetal) and H introduced into a HfO₂ film;

FIG. 14 shows a lattice structure that has bonds of H, Ba (a divalentmetal), and H introduced into a HfO₂ film;

FIG. 15 shows another lattice structure that has bonds of H, Ba (adivalent metal), and H introduced into a HfO₂ film;

FIG. 16 shows yet another lattice structure that has bonds of H, Ba (adivalent metal), and H introduced into a HfO₂ film;

FIG. 17 shows a crystalline structure of a LaAlO₃ perovskite structure;

FIG. 18 shows a crystalline structure that is formed when Ba—H areintroduced into the perovskite structure shown in FIG. 17;

FIG. 19 is a cross-sectional view of a MISFET of Example 1;

FIG. 20 is a cross-sectional view of a MIM capacitor of Example 2;

FIG. 21 is a cross-sectional view of a memory cell transistor of Example3; and

FIG. 22 is a cross-sectional view of a memory cell transistor of Example4.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the embodiment, the course of events for achieving thepresent invention will be described below.

First, the inventors examined metal oxides having high dielectricconstants. A high-dielectric metal oxide tends to contain oxygendefects, and the oxygen defects freely move inside the metal oxide. As aresult, the following problems are caused, according to the results ofthe examination conducted by the inventors.

(1) The oxygen defects that are freely moving easily cause crystalprecipitation from the amorphous structure, and it is difficult tomaintain uniformity in the insulating film characteristics (the problemof phase separation and crystallization).

(2) A defect level appears in the bandgap due to the oxygen defects, andcauses a leakage current (the problem of the leakage current throughoxygen defects).

(3) Structural defects are formed as the oxygen defects move, and thelong-term reliability becomes poorer (the problem of poor reliability).

(4) As electrons are removed from the oxygen defects, the energy isstabilized, and a large threshold voltage (Vth) shift is caused. TheFermi level of the electrode is fixed, and the threshold voltage of thep-type MISFET becomes higher by approximately 0.6 eV and is pinned (theproblem of the pinning of Vth in a p-type MISFET).

Those problems are the problems observed in insulating films, and do notconcern only MISFETs. The insulating film characteristics presentserious problems in an insulating film or a part of the stackedstructure used in flash memory cells or a MIM (Metal-Insulator-Metal)capacitor interposed between metal electrodes.

The inventors next examined cases where nitrogen was added tohigh-dielectric oxides to form HfON, ZrON, HfSiON, ZrSiON, and thelikes. The introduction of nitrogen presents the following problems.

(1) The power of nitrogen to fix oxygen defects is small. Therefore, toprevent crystallization or maintain an amorphous state, a large amountof nitrogen needs to be introduced. If only a small amount of nitrogenis introduced, crystallization is caused, and the insulationcharacteristics are degraded, as is well known.

(2) The bandgap is greatly narrowed by nitrogen. When a large amount ofnitrogen is introduced, the band offset ΔEc with respect to the Sisubstrate on the conduction band side decreases by almost 0.5 eV to 1.0eV. The band offset ΔEv with respect to the Si substrate on the valenceband side also decreases by almost 1.0 eV. As a result, the leakagecurrent becomes much greater than the leakage current in the originalstate.

(3) A problem with the long-term reliability is also caused by nitrogen.Through nitrogen introduction, the number of oxygen defects becomeslarger, but the oxygen defects are not sufficiently fixed. As a result,a structure change is caused by the movement of the oxygen defects overtime. Furthermore, because of the structural change, fixed charges andfixed polarization are caused, and the dielectric characteristics aregreatly degraded.

(4) A compound material of nitrogen and oxygen defects Vo (hereinafterreferred to as “NVoN”) is easily disintegrated. If that happens, thefixed charges are scattered about, and cause a decrease of the mobilityof the carriers traveling through the channel.

(5) If there is excess nitrogen introduction, negative charges aregenerated. This is because nitrogen attracts too many electrons.Depending on the process employed, oxygen defects are easily caused inthe vicinities of nitrogen atoms, and the oxygen defects Vo arepositively charged. Accordingly, the charges generated by the nitrogenintroduction have a possibility to greatly change the threshold voltageVth. Furthermore, since the fixed charges become scattering substances,the mobility might become much lower. If nitrogen is added through heatdiffusion after the formation of a HFSION film, the oxygen defects Voare formed, and an insulating film containing a greater amount ofpositive charges is formed. As a result, the mobility becomes lower, andmore scattering substances appear, though charge compensation isperformed.

(6) In a “NVoN” structure, the level caused by the oxygen defects ispushed out of the gap. However, if electrons are injected into the levelcaused by the oxygen defects, the level returns into the gap. Thispeculiar phenomenon was discovered through the first-principlescalculation performed by the inventors. Although a “NVoN” structureappears to cause the level to disappear from the gap, the level remainsas the electron trap level in the gap.

The inventors next examined aluminate thin films (HfAlO films and thelikes) that have a high degree of expectation for the future. Since Alhas a very small ion radius, phase separation is easily caused. When Alis introduced, a large amount of oxygen defects are also introduced.Therefore, phase separation is easily caused through the mobile oxygendefects, as is known. To maintain an amorphous structure, it isnecessary to introduce a large amount of Al. In doing so, however, thebottom of the conduction band is affected, and the band offset ΔEc withrespect to the Si substrate on the conduction band side greatlydecreases.

Through the course of the above examinations, the inventors studied themethod for completely eliminating the oxygen defects in a metal oxidehaving a high dielectric constant. As a result, the inventors achievedthe following findings.

Typical examples of today's film formation methods for metal oxideshaving high dielectric constants include CVD (chemical vapordeposition), ALD (atomic layer deposition), MBE (molecular beamepitaxy), and a sputtering technique. By any of those methods, whennitrogen is introduced, a large amount of oxygen defects are formed,depending on the nitrogen amount. Although the power of nitrogen to fixthe oxygen defects is small, an appropriate amount of nitrogen should beintroduced, so that the amorphous state of the insulating film can bemaintained through the heating procedure in the manufacturing process.However, due to the nitrogen introduction, the barrier ΔEv against theSi substrate on the valence band side rapidly deteriorates (a decreaseof 0.5 eV to 1.5 eV), and the barrier ΔEc against the Si substrate onthe conduction band side also rapidly deteriorates (a decrease of 0.5 eVto 1.0 eV). As a result, the leakage current becomes much larger thanthe original leakage current observed in a film of a metal oxide.

In a case where Al is introduced, precipitation is easily caused,because Al₂O₃ is stable in terms of energy, and the Al ion radius ismuch smaller than the ion radius of Hf or Zr. If a large amount Al isintroduced, various impurity levels appear in the bandgap, and thedegradation of the insulating film characteristics becomes notablylarge.

In the LSI process, on the other hand, forming gas annealing (FGA) (H₂annealing) is often used. The dangling bonds or the likes in theinterface between the Si substrate and the insulating film areterminated with H, and the reliability degradation mechanism thatdepends on the interface such as NBTI (Negative Bias TemperatureInstability) is stopped. In this manner, it is known the reliability isincreased. However, it is considered that, when hydrogen is introducedinto the insulating film, positive fixed charges are generated (N.Miyata, et al., Applied Physics Letters 86 112906 (2005), for example).As a result, a shift of the threshold voltage Vth occurs, and themobility becomes much lower due to the fixed charges. Therefore, toincrease the reliability, it is necessary to increase the amount ofhydrogen in the vicinity of the interface, and minimize the amount ofhydrogen to be introduced into the film. For example, FGA (H₂ annealing)should be performed for a short period of time at a low temperature, soas to minimize the amount of hydrogen to be introduced into the film. Itis known that, during the H₂ annealing, H₂ does not enter the insulatingfilm, since H₂ is in a stable state as it is. In this manner, in thecase where hydrogen exists in the vicinity of the interface between thesubstrate and the insulating film, the NBTI reliability is increased,while the hydrogen in the film hardly affects the NBTI. As a result,charge centers (fixed charges) appear as described above. Therefore,hydrogen is not introduced into insulating films at present.

As described above, before the inventors made the present invention,there was not a known added material that could completely eliminateoxygen defects in a metal oxide, did not narrow the bandgap, and did notgenerate a level in the gap.

The inventors have made an intensive study on materials to be added tohigh-dielectric metal oxides. As a result, the inventors discoveredthat, if nitrogen and hydrogen were used together as the materials to beadded, an insulating film with desired characteristics could beobtained.

The following is a description of embodiments, with reference to theaccompanying drawings. In the following description, like componentshaving the same functions and structures are denoted by like referencenumerals, and explanation of them is repeated only when necessary.

Embodiments

An insulating film in accordance with an embodiment has a main componentthat is an oxide of a quadrivalent metal (Hf, Zr, or Ti) or a trivalentmetal (La, Y, Sc, Al, or a lanthanum series Ln; Ln being Ce, Pr, Nd, Pm,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). The insulating film is anoxide insulating film having a material of lower valence than thecomponent metal or nitrogen added thereto. An appropriate amount of H isintroduced in accordance with the amount of the added lower-valencematerial or nitrogen.

More specifically, the insulating film of this embodiment is formed byintroducing the same amounts of nitrogen (N) and hydrogen (H) into ahigh-dielectric thin film of a metal oxide. Examples of metal oxidesthat may be used for the high-electric thin film include an oxide of aquadrivalent material (Hf, Zr, or Ti) such as HfO₂, HfSiO₄, ZrO₂,ZrSiO₄, TiO₂, TiSiO₄, a silicate of the oxide of a quadrivalentmaterial, an oxide of a trivalent material (Al, Sc, Y, La, or thelanthanum series Ln) such as LaAlO₃, La₂O₃, Al₂O₃, YAlO₃, Y₂O₃, La₂SiO₅,or LaAlSiO₅, or more particularly,(La₂O₃)_(p)(Y₂O₃)_(q)(Al₂O₃)_(r)(SiO₂)_(s) (each of p, q, r, and s beingzero or a positive real number), a silicate of the oxide of a trivalentmaterial, an oxide of an mixture of a trivalent material and aquadrivalent material such as La₂Hf₂O₇, Y₂Zr₂O₇, LaAlHf₂O₇, orLa₂Hf₂SiO₉, or a silicate of the oxide of the mixture of a trivalentmaterial and a quadrivalent material.

FIG. 1 illustrates the effects that are achieved in a case wherenitrogen is added to a HfO film. In FIG. 1, the abscissa axis indicatesthe nitrogen amount [N], and the ordinate axis indicates the offset ΔEin the energy band with respect to a silicon substrate. In FIG. 1, ΔEvrepresents the offset of the valence band. In a case where only nitrogenis added, the offset ΔEv decreases with an increase of the nitrogenamount, as shown in the graph g₁, and becomes smaller by 0.5 eV to 1.5eV, as mentioned earlier. In a case where the same amounts of nitrogen[N] and hydrogen [H] are added, on the other hand, a decrease in theoffset ΔEv can be prevented, as shown in the graph g₂. If the amount [N]is larger than the amount [H], the point when the offset ΔEv startsdecreasing shifts in the [N] increasing direction, as shown in the graphg₃.

In FIG. 1, ΔEc represents the offset of the conduction band. In the casewhere only nitrogen is added, the offset ΔEc rapidly decreases after theamount [N] becomes larger than 16.7 atomic %, as shown in the graph k₁(the reason for the value “16.7 atomic %” will be described later). As aresult, the offset ΔEc becomes smaller by 0.5 eV to 1.0 eV. In the casewhere the same amounts of nitrogen [N] and hydrogen [H] are added, adecrease in the offset ΔEc can be prevented, as shown in the graph k₂.If the amount [N] is larger than the amount [H], the point when theoffset ΔEc starts decreasing shifts in the [N] increasing direction, asshown in the graph k₃.

Next, the mechanism behind the above characteristics is described. FIGS.2( a) to 2(c) partially show the lower part of the conduction band tothe upper part of the valence band of the density of state (DOS) ofHfON. When the oxygen O of HfO₂ is substituted by nitrogen N, there isan electron shortage, and a hole h (an electron hole) is formed in thevicinity of the top of the valence band (hereinafter also referred to asthe VB), as shown in FIG. 2( a). At this point, oxygen defects Vo areformed. If there are extra electrons e in the vicinities of the oxygendefects Vo, the electrons e occupy the electron hole h in the vicinityof the top of the VB, to reduce the entire energy. This is the mechanismof the occurrence of oxygen defects due to nitrogen introduction, fromthe viewpoint of a micro-level electronic state. In FIG. 2( a), EFrepresents the Fermi level.

At this point, there are serious problems in the electronic state of theinsulating film, as indicated by the dotted lines in FIG. 1. The firstproblem is that the top of the VB becomes higher, and the band offsetΔEv with respect to Si becomes smaller. The second problem is that, whena large amount of nitrogen is introduced, the bottom of the conductionband (hereinafter also referred to as the CB) becomes lower due to theinteraction between the oxygen defects, and the band offset ΔEc withrespect to Si becomes smaller.

Those values with respect to the electronic state, the system energy,and the atomic arrangement were obtained through a first-principlescalculation using a ultrasoft pseudopotential. The calculation was basedon the density functional approach, and was performed through localdensity approximation. The potential of the element used in thiscalculation, such as Hf, Zr, Ti, O, N, H, Ba, Sr, Ca, Mg, La, Y, Sc, Al,and a lanthanum series Ln, has been used in various forms, and provedits high reliability. For example, the lattice constant of HfO₂ obtainedthrough the calculation (a₀=9.55 Bohr=5.052 Angstrom) is smaller thanthe experimental value (9.603 Bohr=5.08 Angstrom) only by approximately0.55%, and is considered to be sufficient. In this embodiment, thecalculation is performed on a fluorite HfO₂ structure. For example, in acase where 96 atomic unit cells of 2a×2a×2a in size with respect to alattice constant a is used, the number of k points used in thecalculation of the Brillouin zone (BZ) is eight, and the energy cutoffis 30.25 Ryd (1 Ryd=13.6058 eV).

As shown in FIG. 2( c), as the oxygen O is substituted by hydrogen H,there is one extra electron, and the electron is added to the vicinityof the bottom of the CB. The electronic state also exhibits notablecharacteristics at this point. Even after the oxygen O is substituted byhydrogen H, there are few changes in the state of the bottom of the CBand the state of the top of the VB. Accordingly, decreases of ΔEc andΔEv can be completely prevented by hydrogen introduction, as indicatedby the solid lines in FIG. 1. If the hydrogen amount is not enough, thedotted lines representing the state of nitrogen in FIG. 1 shift towardthe right-hand side, as there is extra nitrogen (the graphs g₁ and k₁shift to the graphs g₃ and k₃).

As shown in FIG. 2( a), when nitrogen is introduced, the oxygen defectsVo are formed, and the entire system is stabilized. Likewise, it ispossible to stabilize the entire system by filling the electron hole hat the top of the VB caused by nitrogen substitution with the electron e(FIG. 2( c)) at the bottom of the CB caused by hydrogen substitution.FIG. 2( b) shows the final electronic state. In FIG. 2( b), there arealmost no decreases of ΔEc and ΔEv. Particularly, the increase of ΔEvdue to the nitrogen is stabilized, pulled down by the electronic stateof the hydrogen. Thus, a decrease of ΔEv is prevented. In FIG. 2( b), Egrepresents the bandgap of the HfON film formed by the addition of H andN.

As shown in FIG. 2( a), when there is no hydrogen, HfON has oxygendefects, and forms “NVoN” structures. As a result, the system isstabilized. At this point, the inner-gap state caused by the oxygendefects is pulled out of the gap. However, when electrons are introducedinto the system, the state reappears in the gap, and traps the electronsto stabilize the system. This was found by the first-principlescalculation performed by the inventors. This trap is an intermediatestate of trap assist tunneling (TAT). Therefore, to maintain theinsulating film valid, a new upper limit needs to be set for the stateor the number of oxygen defects. The number of oxygen defects needs tobe 1 or less for each unit of 2a×2a×2a, and more preferably, is 1 orless for each unit of 3a×3a×3a, with the spread of the trap level beingtaken into account. This can be determined by checking whether the bandappearing in the gap in the band structure has a wider dispersion thanthe bandgap. There is almost no dispersion in each 2a×2a×2a unit, andthe dispersion becomes 5% or less of the bandgap. Accordingly, there arealmost no interactions with the neighboring units. The dispersionbecomes none in each 3a×3a×3a unit, and becomes 1% or less of thebandgap (becomes flat level). Accordingly, there are no interactionswith neighboring units.

In terms of atomic %, the oxygen defects in this unit cell is 1.1 atomic% or less, and more preferably, is 0.31 atomic % or less. This isexpressed by the following relationship. Where [N] atomic % representsthe nitrogen amount and [H] atomic % represents the hydrogen amount, itis preferable that the following equation is satisfied:

{[N]−[H]}/2≦1.1 atomic %

It is more preferable that the following equation is satisfied:

{[N]−[H]}/2≦0.31 atomic %

Here, {[N]−[H]}/2 is equal to the amount of oxygen defects. Although theabove relationships involve nitrogen, the same upper limit appears whenanother added material is used.

If the above amounts [N] and [H] are converted into densities (cm⁻³), itis preferable that the following relationship is satisfied:

{[N]−[H]}/2≦1.0×10²¹ cm⁻³

It is more preferable that the following relationship is satisfied:

{[N]−[H]}/2≦3.0×10²⁰ cm⁻³

Hereinafter, the same expression unit is used in each one numericexpression.

The above amounts are expressed both in atomic % and density, becausethe former can be easily understood as the number of added materialatoms in each unit, and the latter can be easily applied to any otheroxide. With the interaction between the added materials being taken intoaccount, the densities of the added materials in an oxide determine thecharacteristics of the resultant structure. As the densities of theadded materials are higher, the interaction between the added materialsis clearly larger. Therefore, amounts expressed in density can be morewidely understood than amounts expressed in atomic %.

The relationships among the unit size of HfO₂, the percent expression,and the density expression are now described. The fundamental structureof HfO₂ is a so-called calcium fluoride structure that has aface-centered cubic (FCC) lattice formed by Hf serving as the cations,and a simple cubic (SC) lattice formed by O serving as the anions, asshown in FIG. 3. There is four-unit HfO₂ in the unit of a×a×a shown inFIG. 3. More specifically, there are four (=8×1/8+6×1/2) Hf atoms andeight (=8×1) O atoms in the a×a×a unit. If there is one oxygen defect,the atomic percent becomes 1÷12×100 atomic %=8.33 atomic %, since theoxygen defect is one of the twelfth atoms. Also, as the lattice constanta is approximately five angstroms, the atomic percent can be convertedinto the density: 1÷(5 angstroms×5 angstroms×5 angstroms)=8.0×10²¹ cm⁻³.In this manner, the atomic % expressions and the density expressionswith respect to the respective unit cell sizes in a case where one ofthe atoms is substituted are as follows:

TABLE one atom in unit atomic % one-atom density a × a × a 8.33 at % 8.0× 10²¹ cm−³ 2a × 2a × 2a  1.1 at % 1.0 × 10²¹ cm−³ 3a × 3a × 3a 0.31 at% 3.0 × 10²⁰ cm−³ 4a × 4a × 4a 0.13 at % 1.3 × 10²⁰ cm−³ 4.3a × 4.3a ×4.3a 0.11 at % 1.0 × 10²⁰ cm−³ 5a × 5a × 5a 0.07 at % 6.4 × 10¹⁹ cm−³ 6a× 6a × 6a 0.04 at % 3.7 × 10¹⁹ cm−³

FIGS. 4( a) to 4(d) schematically show the process in which hydrogen isincorporated into HfON. When nitrogen is introduced into HfO₂, oxygendefects Vo are formed, with the ratio between the nitrogen and theoxygen defects being 2:1. The entire system is then stabilized (see FIG.4( a)).

As described above, the fundamental structure of HfO₂ is a so-calledcalcium fluoride structure that has a face-centered cubic (FCC) latticeformed by Hf serving as the cations, and a simple cubic (SC) latticeformed inside by O serving as the anions. The oxygen defects Vo, thenitrogen N, and the hydrogen H substitute the oxygen (anions) positions,and Al, La, Mg, Ba, and the likes substitute the Hf (cations) positions.

When N is incorporated into the fundamental structure of HfO₂, a “NVoN”structure (nearest neighbor structure) in which two N atoms becomeclosest to oxygen defects Vo may be formed as shown in FIG. 5, or a“NVo+N” structure (second-neighbor structure) in which one N atom is faraway from oxygen defects Vo may be formed as shown in FIG. 6. The energydifference between the two structures is approximately 0.2 eV. It isnatural to consider that the oxygen defects Vo are formed adjacent toone of the nitrogen atoms, and supply electrons to the other one of thenitrogen atoms. If hydrogen H is introduced from outside at this point,the hydrogen is absorbed at the locations of the oxygen defects Vo (FIG.7), and an energy gain is obtained, as is apparent through thefirst-principles calculation. As a result, there is an electron shortagein the electronic state (FIG. 4( b)). Further, H and N become adjacentto each other, and form a pair, as shown in FIG. 7.

Since it has become apparent that a pair of a nitrogen atom and ahydrogen atom becomes stabilized through an exchange of electrons (FIG.2( b)), there is an extra nitrogen atom, with the pair of a nitrogenatom and a hydrogen atom being excluded (FIG. 4( b)). The two extranitrogen atoms cause one oxygen defect Vo through the same mechanism asabove. At this point, oxygen (O₂/2) is released, and a low-dielectriclayer or the like is formed. Therefore, it is preferable to form astructure that can release oxygen to the outside in the hydrogenintroduction process. The energy gain during the process of releasingoxygen and absorbing hydrogen is very large.

The above process is repeated to have the same amounts of nitrogen N andhydrogen H at last. Hydrogen H has the highest possibility to becomeadjacent to nitrogen N and form a pair, and at that point, is in themost stable condition (FIG. 4( d)). If the hydrogen amount is not enough(FIG. 4( c)), the process is suspended, and attention is required as thenumber of electrons does not match in the suspended state. Even in sucha case, the oxygen defects Vo are formed, and, if the heating process toform the structure shown in FIG. 2( a) is carried out, the above “NVoN”structure can be formed. In this manner, the number of electrons can beadjusted. However, since oxygen is released while the oxygen defects Voremain, the intermediate state of trap assist tunneling (TAT) appears asdescribed above.

(Example Film Formation 1)

FIGS. 8A and 8B show a first film formation example about a HfONH filminto which the same amounts of hydrogen and nitrogen are to beintroduced. A HfO₂ film is formed by CVD on a silicon substrate 1subjected to device isolation and channel doping (phosphorus P or boronB are introduced, for example). Plasma nitridation is then performed onthe HfO₂ film at room temperature, to form a HfON film 2. After that,plasma hydrogenation (60 seconds at room temperature) or hydrogenationusing excited hydrogen (also 60 seconds at room temperature) isperformed to introduce hydrogen that is excited in an atomic state (FIG.8A), and form a HfONH film 2. After that, PDA (Post DepositionAnnealing) is performed in a vacuum at 900° C. for 60 seconds. Throughthose procedures, the relationship, {[N]−[H]}/2≦1.1 atomic % (or{[N]−[H]}/2≦1.0×10²¹ cm⁻³ in terms of density), is sufficientlysatisfied. {[N]−[H]}/2 represents the amount of oxygen defects (in thesame expression unit as that of the right side). By measuring the filmby STS (scanning tunneling spectroscopy), for example, it is possible todetermine whether oxygen defects remain in the film or are buried inhydrogen. The temperature and the processing time of the PDA are set sothat the hydrogen atoms are scattered in the film.

The plasma hydrogenation (excited hydrogenation) is performed at roomtemperature and is extended to 100 seconds, so as to maintain therelationship, {[N]−[H]}/2≦0.31 atomic % (or {[N]−[H]}/2≦3.0×10²⁰ cm⁻³ interms of density). In the plasma hydrogenation procedure, it isessential to take a long time, so as to introduce a sufficient amount ofhydrogen atoms into the film. However, if the plasma hydrogenation takestoo long a time, poor efficiency becomes a problem. Therefore, theplasma hydrogenation procedure is carried out at room temperature for100 seconds.

Also, to perform the PDA at a low temperature, a long period of timeshould be taken. For example, by performing the PDA at 600° C. for 180seconds, extra hydrogen atoms and oxygen defects can be sufficientlyreduced. It is possible to determine whether extra hydrogen atoms andoxygen atoms have been reduced to sufficiently small amounts with highprecision, through the above STS measurement, the TAT level measurementin a MOSFET, light absorption measurement, or the like. At this point,the extra hydrogen atoms and the remaining oxygen gas O₂ used for thehydrogen atom introduction are released from the HfONH film 2 to theoutside of the film (FIG. 8B). The plasma hydrogenation or excitedhydrogenation is the process to introduce atomic hydrogen, and the PDAis the process to facilitate the dispersion of the atomic hydrogen andthe release of extra hydrogen and oxygen.

An electrode (made of a metal material TiN or polysilicon, for example)is then formed. After that, ion implantation (P or B ions) is performedin the case of a polysilicon electrode, at the same time as the gateformation, the sidewall formation, and the ion implantation into thesource and drain regions, though not shown in the drawing. Spikeannealing at 1050° C. is performed, and H₂ sintering is performed, so asto form a MISFET (MOSFET). In the film, H and N form pairs, and are in astable state. Therefore, when H₂ sintering is performed, the hydrogen,nitrogen, or oxygen is not released from the insulating film. Also,since there are no oxygen defects in the insulating film, no morehydrogen is introduced into the film.

In the H₂ sintering, hydrogen is not in an atomic state, but exists asstable H₂ molecules. Therefore, it is difficult to fill the alreadystable oxygen defects such as “NVoN”, “LaVoLa”, “AlVoAl”, or “MgVo” withhydrogen. Rather, such oxygen defects are formed to create those stablestructures (see JP-A 2007-273587 (KOKAI), for example). If H₂ sinteringis performed on a film of HfON, HfLaO, HfAlO, HfMgO, or the like priorto stabilization, oxygen defects Vo are formed, and the film isstabilized. At this point, oxygen is released. Therefore, if H₂sintering is performed after the electrode formation as described above,an interfacial low-dielectric layer is formed, and the layer thicknessbecomes larger.

In the first film formation example of this embodiment, on the otherhand, hydrogen excited in an atomic state is introduced into the filmduring the hydrogen introduction process using plasma hydrogen orexcited hydrogen. In this case, the hydrogen is easily absorbed at theoxygen defects, and a stable state is formed. Furthermore, theabsorption can be caused at a low temperature.

The above film formation process has the following points to whichattention needs be paid.

(1) It is necessary to introduce a large amount of hydrogen into thegate insulating film. Immediately after hydrogenation, a larger amountof hydrogen than the amount of nitrogen is introduced, so that theamount of hydrogen becomes equal to the amount of nitrogen in theprocess illustrated in FIGS. 4( a) to 4(d). Accordingly, the entire filmapproaches the most stable state. Extra hydrogen excited in an atomicstate is released to the outside. Where there is extra hydrogen excitedin an atomic state, the temperature is preferably 950° C. or lower. Thisis because, if the temperature exceeds 950° C., there is a probabilitythat oxygen is substituted by interstitial hydrogen excited in an atomicstate. After the extra hydrogen excited in an atomic state is releasedto the outside at 950° C. or lower, the temperature can be increased to950° C. or higher. Accordingly, not a problem is caused if an electrodeis formed by performing spike annealing at 1050° C. Since hydrogen canbe dispersed at a low temperature, the extra hydrogen excited in anatomic state can be released to the outside at 400° C. or lower.Although high-temperature processing is more efficient timewise, theextra hydrogen might be released to the outside at 400° C., if thestructure or process that does not exhibit high heat resistance isemployed. In this aspect, hydrogen greatly differs from fluorine. It isdifficult to release fluorine through a low-temperature process at 400°C., and extra fluorine becomes fixed charges. It is also difficult tointroduce atomic F into the film, since F has high reactivity. As aresult, F is introduced through ion implantation, and it is much moredifficult to introduce a desired amount of fluorine to an optimumlocation than hydrogen.

(2) In a case where the hydrogen amount is not enough, there is ashortage of electrons due to nitrogen introduction. To compensate forthe shortage with oxygen defects, the temperature needs to be 500° C. orhigher, after nitrogen is introduced. More specifically, oxygen defectsVo equivalent to {[N]−[H]}/2 are formed, and oxygen molecules equivalentto {[N]−[H]}/4 are released (half the amount of oxygen defects, with oneoxygen molecule being formed with two oxygen atoms). Accordingly,excellent insulation characteristics can be achieved. In connection withthe oxygen release, attention needs to be paid, so as not to form alow-dielectric layer, as described above. Attention also needs to bepaid to the upper limit of the oxygen defects Vo as already mentioned.

(Example Film Formation 2)

To form a metal oxide film, there are various known methods other thanthe above CVD method. For example, any kind of technique, such as avapor deposition technique, a sputtering technique, or an ALD (atomiclayer deposition) technique can be used. In a case where plasma nitrogenand hydrogen excited in an atomic state are simultaneously introducedinto an insulating film while the insulating film is being deposited,the temperature may be low. During the formation of a HfO₂ film, thefilm is left in a mixed gas of an excited hydrogen gas, an argon gas,and an excited nitrogen gas, and low-temperature heating is performed(at 100° C.). In this manner, hydrogen and nitrogen can besimultaneously introduced into the gate insulating film HfO₂.Alternatively, plasma nitrogen and hydrogen excited in an atomic statemay be alternately introduced. It is also possible to introduce nitrogenand hydrogen simultaneously, together with a NH₃ gas, excited oxygen,plasma hydrogen, or the like. In this case, the nitrogen amount and thehydrogen amount are maintained at the same level since the initial stageof the film formation, which differs from the first film formationexample in which hydrogen is introduced after nitrogen introduction.Accordingly, this example has the great advantage that the filmformation can be carried out while the most stable structure is beingformed. In this case, the process of releasing oxygen from a HfO₂ filmis not required, and a HfONH film can be formed even in the initialstage. If the process of releasing oxygen is carried out as in a casewhere hydrogenation is performed later, it is necessary to performhydrogenation before another film is formed on the insulating film. Ifthe oxygen releasing process is not required, the later procedures canbe readily arranged.

(Remarks on Optimum Amounts)

Next, the optimum amounts to be set in a case where hydrogen H andnitrogen N are both added to an ionic oxide insulating film made of ametal and oxygen are described. First, the hydrogen amount [H] should besmaller than or almost equal to the nitrogen amount [N]. The amount ofoxygen defects Vo is half the amount of nitrogen that is not paired withhydrogen, and accordingly, is {[N]−[H]}/2. If the amount of oxygendefects Vo becomes 8.33 atomic % or more, an interaction is caused amongthe oxygen defects Vo, and a band formed by the oxygen defects Voappears in the bandgap. As a result, the band offset ΔEc becomes lower.Therefore, 8.33 atomic % (8.0×10²¹ cm⁻³ in density) is the first upperlimit.

Meanwhile, {[N]−[H]} may be zero or a positive value. This is becauseextra hydrogen introduction into the film can be prevented by devising afilm formation process. Accordingly, {[N]−[H]} should be sufficientlylarger than at least −1.0 atomic %.

In view of this, the following relationship is satisfied in thisembodiment:

−1.0 atomic %≦{[N]−[H]}/2≦8.33 atomic %

More preferably, the following relationship is satisfied:

−0.1 atomic %≦{[N]−[H]}/2≦7.4 atomic %

{[N]−[H]}/2 may be zero or a positive value in the neighborhood of zero,and should be 7.4 atomic % or less at a maximum. This is because, if{[N]−[H]}/2 exceeds 7.4 atomic %, the decrease of the offset ΔEc becomesmuch larger, as shown in FIG. 9. The reason for the sudden largedecrease is that a virtual intermediate state appears in the gap due tothe interaction between the oxygen defects.

Oxygen defects characteristically trap electrons. Therefore, if thereare a larger amount of oxygen defects than 1.1 atomic % (1.0×10²¹ cm⁻³in density), the oxygen defects might conduct electricity while trappingelectrons. Therefore, it is more preferable to restrict the amount ofoxygen defects to 1.1 atomic % or less.

As already mentioned with reference to FIG. 2( a), when electrons areinjected into a “NVoN” structure, a state reappears in the gap, andtraps electrons for stabilization. The trapping is the intermediatestate of trap assist tunneling (TAT). Therefore, the oxygen defects needto be eliminated as much as possible. With the spread of the trap levelbeing taken into account, it is preferable that the number of oxygendefects is 1 or less for each unit of 2a×2a×2a (where the dispersionbecomes almost none, and the dispersion width is 1% or less of thebandgap), and it is more preferable that the number of oxygen defects is1 or less for each unit of 3a×3a×3a (where the dispersion becomes none,and the dispersion width is 0.2% or less of the bandgap). Therefore, thenumber of oxygen defects is 1.1 atomic % or less, and more preferably,is 0.31 atomic % or less. In density, the oxygen defects is 1.0×10²¹cm⁻³ or less, and more preferably, is 3.0×10²⁰ cm⁻³ or less.

Further, from the standpoint of the structure, the followingrelationship should be satisfied:

0.0 atomic %≦[N]+[H]≦50.0 atomic %

If the sum of [N] and [H] exceeds 50.0 atomic %, the oxygen amountrapidly decreases, and it becomes difficult to maintain the structure.To maintain a high dielectric constant as an oxide, the oxygen amountshould preferably be half or more than the oxygen amount (66.7 atomic %)in the parent structure, or be 33.3 atomic % or more. Accordingly,desired dielectric characteristics are maintained, if the followingrelationship is satisfied:

0.0 atomic %≦[N]+[H]≦33.4 atomic %

Further, nitrogen might be first introduced during the film formationprocess. Through experiments, it has become apparent that an amorphousstate cannot be maintained unless the amount of nitrogen introduced intoa HfO₂ film or the like is 16.7 atomic % or more. In such a case, the“NVoN” structures serve as pins for restricting structural changes. Thenumber of “NVoN” structures is the same as the amount of oxygen defects,which is 8.33 atomic % (=16.7/2 atomic %). The N—H pairs are alsoconsidered to serve as pins, and the number of those pairs is equal tothe hydrogen amount [H]. Therefore, it is preferable that the sum of [H]and the oxygen defects {[N]−[H]}/2 that are not paired is 8.33 atomic %or more. In short, the following relationship is satisfied:

16.7 atomic %≦[N]+[H]

In the case where nitrogen is first introduced, and H is thenintroduced, the nitrogen amount needs to be 16.7 atomic % or more, asdescribed above. However, in a case where H and N are simultaneouslyintroduced since the initial stage of the film formation, it is notnecessary to introduce a large amount of nitrogen. In this case, thenitrogen amount [N] should be equal to the hydrogen amount [H].

As described above, it is most preferable that [N] and [H] are the same.The errors in measurement by the secondary ion mass spectrometry (SIMS)vary with materials and are very large. FIG. 10 shows data that wereanalyzed through SIMS. The semiconductor device subjected to theanalysis has a structure in which a HfONH film was formed on a Sisubstrate through the film formation process of this embodiment, and ametal electrode (such as a TaC electrode) was formed on the HfONH film.As can be seen from the analysis results shown in FIG. 10, [N] and [H]in the HfONH film satisfy the following relationship:

−1.0 atomic %≦[N]−[H]≦1.0 atomic %

where the distribution forms are almost the same. If precise measurementis possible, it is more preferable that the following relationship issatisfied:

−0.1 atomic %≦[N]−[H]≦0.1 atomic %

Through the film formation process of this embodiment, it is possible inprinciple to satisfy the relationship, [N]≧[H].

As already mentioned, STS measurement can determine whether “there areoxygen defects Vo” or “hydrogen is trapped by the oxygen defects Vo”.The energy level of the oxygen defects Vo does not exist in the gap whenthe charges are neutral, but the energy level returns into the gap whenelectrons are injected. On the other hand, if hydrogen is buried in theoxygen defects, a state (a level) does not appear in the gap even ifelectrons are injected. By measuring the difference, the amount ofoxygen defects can be determined.

Also, changes in the electronic state can be observed in detail throughXPS (X-ray Photoelectron Microscopy). In a HfONH film, not only Hf—Obonds but also Hf—N bonds and Hf—H bonds are formed, and distributionsof the respective kinds of bonds are formed. Accordingly, remarkablechanges occur in the Hf spectrum.

(Upper Limit and Lower Limit of Nitrogen Amount)

Next, the upper limit and the lower limit of the nitrogen amount in aninsulating film are described. First, the upper limit is explained.

A nitride film is formed while NVN structures are formed. Morespecifically, two nitrogen atoms exist for one oxygen defect Vo, andhydrogen fills the oxygen defect. If one NHNH structure (formed with twoN—H pairs) or more exist in a unit of a×a×a, the interaction withadjacent units becomes very large, and the band offset ΔEv on thevalence band side becomes smaller. To avoid this, the nitrogen amountshould be 16.7 atomic % or less (1.6×10²² cm⁻³ or less in density). Thelevel of the valence band side tends to be localized. Therefore, even ina case where one NHNH structure exists in a unit of a×a×a, thedecreasing rate of the band offset ΔEv is restricted to approximately10% of ΔEv, as is apparent from calculations performed by the inventors.However, if the nitrogen amount becomes larger than 16.7 atomic %, theband offset ΔEv rapidly decreases, and it becomes difficult to maintainthe insulation characteristics against holes.

Likewise, in a case where one NHNH structure (formed with two N-H pairs)or less exists in a unit of 2a×2a×2a, the interaction with adjacentunits can be prevented, and the band offset ΔEv of the valence band sidehardly decreases, as is apparent from calculations performed by theinventors. The decrease amount is almost 2%. Therefore, by setting thenitrogen amount at 2.2 atomic % or less (2.0×10²¹ cm⁻³ or less indensity), the band offset ΔEv of the valence band side can be preventedfrom decreasing.

In the above description, the interaction of the state in the vicinityof the top of the valence band due to the nitrogen addition has beendescribed. The added material is not necessarily nitrogen, and the sameeffects as above can be achieved with some other added material.Particularly, the amount converted into density is valid for any oxide,as the density may be considered as the density of the added material inan oxide. However, attention needs to be paid, because a difference ininitial amount of addition is caused, depending on the stable structuresformed with the added material and oxygen defects. In the case ofnitrogen, one structure is formed with two nitrogen atoms and one oxygendefect. Likewise, in a case where a trivalent material such as Al or Lais introduced into an oxide of a quadrivalent material, one stablestructure is formed with two Al (or La) atoms and one oxygen defect. Ina case where a divalent material such as Ba or Mg is introduced into anoxide of a trivalent material, one stable structure is formed with twoBa (Mg) atoms and one oxygen defect. Accordingly, if the amount of theaddition is 1.6×10²² cm⁻³ or less, or more preferably, is 2.0×10²¹ cm⁻³or less, a decrease of the band offset ΔEv on the valence band side canbe prevented. In a case where a divalent material such as Ba or Mg isintroduced into an oxide of a quadrivalent material, on the other hand,one stable structure is formed with one Ba (Mg) atom and one oxygendefect Vo. For example, a Ba-Vo structure is formed. In such a case, theoptimum density is half the density in each of the other cases, and, ifthe amount of the addition is 0.8×10²² cm⁻³ or less, or more preferably,is 1.0×10²¹ cm⁻³ or less, a decrease of the band offset ΔEv on thevalence band side can be prevented.

Next, the lower limit is described. In this embodiment, nitrogen andhydrogen are distributed in a HfO₂ film, and the effect to gain entropycan be expected through the distribution. Without the distribution,oxygen defects are formed, and entropy is obtained through distributionof the oxygen defects. At a high temperature of 1050° C. or more, alarge amount of oxygen defects are formed, and, if there is one or morenitrogen atoms existing in a 3a×3a×3a unit, the distribution of theoxygen defects can be overcome. Accordingly, control can be performedwith the use of nitrogen and hydrogen. In short, 0.31 atomic % (3.0×10²⁰cm⁻³ in density) or more of nitrogen is sufficient. In a case where ashort-time heat treatment is carried out for about 30 seconds at a lowtemperature of 600° C. or less, the distribution of oxygen defects canbe overcome if one nitrogen atom exists in a 5a×5a×5a unit. Accordingly,control can be performed with the use of nitrogen and hydrogen. Inshort, 0.067 atomic % (6.4×10¹⁹ cm⁻³ in density) or more of nitrogen issufficient. To sum up, if at least 0.067 atomic % (6.4×10¹⁹ cm-3 indensity) or more of nitrogen, or more preferably, 0.31 atomic %(3.0×10²⁰ cm⁻³ in density) or more of nitrogen is added, an insulatingfilm with excellent characteristics without oxygen defects can beformed. Therefore, it is preferable that the nitrogen amount [N]satisfies the following relationship:

6.4×10¹⁹ cm⁻³≦[N]≦1.6×10²² cm⁻³

Since the hydrogen amount [H] should preferably be approximately thesame as the nitrogen amount [N], it is preferable that the hydrogenamount [H] satisfies the following relationship:

6.4×10¹⁹ cm⁻³≦[H]≦1.6×10²² cm⁻³

It is more preferable that the nitrogen amount [N] satisfies thefollowing relationship:

3.0×10²⁰ cm⁻³≦[N]≦2.0×10²¹ cm⁻³

and it is also more preferable that the hydrogen amount [H] satisfiesthe following relationship:

3.0×10²⁰ cm⁻³≦[H]≦2.0×10²¹ cm⁻³

In this specification, the state in which the hydrogen amount [H] andthe nitrogen amount [N] are approximately the same indicates that thedifference {[N]−[H]} between the nitrogen amount [N] and the hydrogenamount [H] is less than 10% of 6.4×10¹⁹ cm⁻³, which is the lower limitof the nitrogen amount [N]. Accordingly, the following relationship issatisfied:

0≦{[N]−[H]}<0.1×6.4×10¹⁹ cm⁻³

In view of this, the lower limit of the hydrogen amount [H] is definedas follows:

[H]>6.4×10¹⁹ cm⁻³−0.1×6.4×10¹⁹ cm⁻³=5.76×10¹⁹ cm⁻³

In the above description, the entropy obtained with an added materialhas been described. However, the added material is not necessarilynitrogen, and the same effects as above can be achieved with some otheradded material. Particularly, the added material should only have thedensity to generate the same size of distribution, as the density may beconsidered as the density of oxygen defects. The amount converted intodensity is valid for any oxide. Accordingly, if at least 6.4×10¹⁹ cm⁻³or more, or more preferably, 3.0×10²⁰ cm⁻³ or more of an added materialis added, oxygen defects are not formed, and an insulating film withexcellent characteristics can be formed.

In the above description, the cases at different temperatures have beendescribed. Those cases involve an important difference in terms ofsemiconductor device production. In a case where the source and drainare activated after a gate insulating film is formed, the gateinsulating film is subjected to activation annealing at approximately1050° C. In this case, it is necessary to add a certain amount ofadditional material to the gate insulating film. In a case where a gateinsulating film is formed after the activation of the source and drain,on the other hand, the gate insulating film is not subjected to ahigh-temperature treatment for the activation. Accordingly, the amountof material to be added to the gate insulating film can be reduced.Typical examples of such gate insulating films include buried gates ordamascene gates. However, this process is valid for all types ofprocedures for forming a gate insulating film only through alow-temperature treatment.

Referring now to FIGS. 11A and 11B, a method for forming a damascenegate is described. First, as shown in FIG. 11A, a dummy gate insulatingfilm 12 and a dummy gate electrode 13 are formed on a silicon substrate11. With the dummy gate electrode 13 serving as a mask, impurities areintroduced into the silicon substrate 11, to form extension regions 14.After that, gate sidewalls 15 formed with insulating films are providedat the side portions of the dummy gate electrode 13. With the gatesidewalls 15 and the dummy gate electrode 13 serving as masks,impurities are introduced into the silicon substrate 11, so as to formsource and drain regions 16. A heat treatment is then carried out toactivate the introduced impurities. After that, an interlayer insulatingfilm 17 is deposited, and a flattening operation is performed to exposethe upper face of the dummy gate insulating film 13 (FIG. 11A). Thedummy gate electrode 13 and the dummy gate insulating film 12 areremoved, so as to form a concave portion having a bottom face throughwhich the upper face of the silicon substrate 11 is exposed. A gateinsulating film 18 is then formed to cover the bottom face and the sidefaces of the concave portion, and a gate electrode 19 is formed on thegate insulating film 18 to fill the concave portion. As described above,by the method for manufacturing a semiconductor device having adamascene gate, the insulating film 18 does not need to be subjected tohigh-temperature annealing for activation.

Next, materials that can be used as added materials in place of nitrogenare described.

As described above, nitrogen plays an important role when hydrogen isintroduced into an insulating film. However, it is possible to achieveexactly the same effects as above by introducing cations (positive ions)with lower valence than the metal serving as a parent structure of ametal oxide. This is now described in the following.

In this embodiment, oxygen defects are formed due to nitrogen, andhydrogen is buried in the oxygen defects. The entire insulating film isthen stabilized. However, there is also a process in which a low-valencemetal element is introduced to form oxygen defects, and hydrogen atomsare buried in the oxygen defects. The first-principles calculation hasmade it clear that the entire structure turns into a most stablestructure through the process. A case where aluminum Al, instead of Hf,is introduced into a HfO₂ film is now described. FIGS. 12( a) to 12(c)show the results of the experiment, and the results are very much likethe results obtained in the case of nitrogen (FIGS. 2( a) to 2(c)).

As shown in FIG. 12( a), only three electrons are released in the caseof Al, though four electrons are released in the case of Hf. As aresult, the case of Al is short by one electron, and an electron hole (ahole h) is formed on the top of the valence band (VB). At this point,oxygen defects Vo are formed. If there is an extra electron e, theelectron fills the electron hole h in the vicinity of the top of the VB.Accordingly, the entire energy becomes lower. This is the mechanism ofthe formation of oxygen defects caused by Al introduction, from theviewpoint of a micro electronic state. FIG. 12( c) shows a stateobserved in a case where only H is added.

If a large amount of Al is introduced, phase separation might be causeddue to the difference in lattice constant. This is regarded as aphenomenon caused by oxygen defects that move around freely. As shown inFIG. 12( b), hydrogen fills up the oxygen defects. Therefore, even whena large amount of Al is introduced, phase separation can be avoided.Phase separation triggered by displacement of oxygen defects is alsocaused in a case where a low-valence element having a large ion radius,such as La. However, even when La is introduced, phase separation canalso be avoided through the same mechanism as that used in the case ofAl. The avoidance of phase separation is one of the effects achieved byeliminating oxygen defects by hydrogen introduction.

At this point, the band offsets ΔEc and ΔEv also become better thanthose in the case of nitrogen. In the case of nitrogen, the band offsetΔEv is increased due to the nitrogen. In the case of Al, the increase isnot caused, and there is not a problem with the band offset ΔEv.Further, since the energy level of H exists lower than the energy levelof oxygen, the entire energy is pulled downward (FIG. 12( b)).Accordingly, the band offset ΔEv becomes larger, and bettercharacteristics are achieved. However, the cause of the decrease of theband offset ΔEc is the oxygen defects, which is exactly the same as thecause of the decrease in the case of nitrogen. Accordingly, the range ofthe band offset ΔEc is exactly the same as that in the case of nitrogen.To sum up, it is preferable that the amount of oxygen defects is equalto or smaller than 1.1 atomic % (1.0×10²¹ cm⁻³ in density), and it ismore preferable that the amount of oxygen defects is equal to or smallerthan 0.31 atomic % (3.0×10²⁰ cm⁻³ in density).

FIG. 13 shows a structure obtained in a case where Al (a trivalentmetal) is added to HfO₂. One of the Hf atoms is substituted by Al, and Hfills up an oxygen defect. Al and H become adjacent to each other andform a pair. As will be described later with reference to FIG. 18, aBa—H pair or the like in LaAlO₃ (a trivalent parent metal) is also a 1:1pair. FIG. 14 shows a structure observed in a case where Ba as adivalent metal element is introduced into HfO₂. This structure has acombined form of H, Ba, and H adjacent to one another. Another examplestructure of the structure shown in FIG. 14 is has H, Ba, and H alignedalmost in a straight line. FIG. 15 shows such an example structure. Ifone of the H atoms exists in an oxygen position in an adjacent unitcell, this structure is formed. As shown in FIG. 16, the oxygen existingon a diagonal line in the same plane formed with oxygen might bereplaced with H. Since eight oxygen atoms exist at equal intervals andsurround Ba, two of the oxygen atoms are replaced with H.

To achieve the effects of this embodiment, {[Al]−[H]}/2 should be 8.33atomic % or less, since the amount of oxygen defects should be{[Al]−[H]}/2. To maintain the structure as a dielectric structure, thehydrogen amount [H] should be half or less than half the oxygen amount,or 33.4 atomic % or less, since [H] replaces the oxygen position. Tomaintain the structure as a dielectric structure, the aluminum amount[Al] should be half or less than half the Hf amount, or 16.7 atomic % orless, since [Al] replaces the Hf positions. The optimum amount is stillachieved when [Al] is equal to [H]. This value is considered to be thevalue obtained when two Al atoms are introduced into an a×a×a unit. Withthe interaction between Al atoms being taken into consideration, theinteraction becomes stronger and affects the valence band VB when two ormore Al atoms are introduced into a 2a×2a×2a unit. In this case, theoffset on the VB side tends to become larger. This increase is aneffective increase to restrict the leakage to be caused by holes, butleads to a decrease in dielectric constant. Therefore, it is desirablethat two or less Al atoms (or some other low-valence material) areintroduced into a 2a×2a×2a unit. To sum up, the amount of the materialto be added to HfO₂ should be equal to or smaller than 16.7 atomic %(1.6×10²² cm⁻³ in density), and more preferably, be equal to or smallerthan 2.2 atomic % (2.0×10²¹ cm⁻³ in density).

Further, with entropy being taken into consideration, it is preferablethat the lower limit of the amount of [trivalent element] is equal to orlarger than 6.4×10¹⁹ cm⁻³, and it is more preferable that the lowerlimit of the amount of [trivalent element] is equal to or larger than3.0×10²⁰ cm⁻³, as already mentioned. To sum up, in an oxide of aquadrivalent metal, it is preferable that the following relationship issatisfied:

6.4×10¹⁹ cm⁻³≦{trivalent element}≦1.6×10²² cm⁻³

and it is more preferable that the following relationship is satisfied:

3.0×10²⁰ cm⁻³≦{trivalent element}≦2.0×10²¹ cm⁻³

As for the substitution, the essential condition for maintaining adielectric structure is that the substitution is restricted to half orless than the amount of position ions (cations) and the amount ofnegative ions (anions). Some examples are now described. Since HfO₂ isformed with 33.3 atomic % of cations and 66.7 atomic % of anions, therespective upper limits are 16.7 atomic % and 33.4 atomic %, which arehalf the cation and anion amount.

FIGS. 17 and 18 show the structures of LaAlO₃ as perovskite structures.Since the cations to be substituted are La and Al (FIG. 17), the amountsof cations are 20 atomic % each, and the amount of anions is 60 atomic%. Accordingly, (10+10) atomic % and 30 atomic % are the respectiveupper limits. For example, in a case where Ba and H are introduced intoLaAlO₃ (FIG. 18), the following conditions should be satisfied:0≦[Ba]≦20 atomic % (largest), and 0≦[H]≦30 atomic %. In this case, Ba isintroduced in place of a trivalent metal element La or Al, and H isintroduced in place of O. To prevent a decrease of the dielectricconstant, it is preferable that the Ba amount (or Mg, Ca, or Sr amount)is equal to or less than the amount of added Al in the HfO₂. Thisapplies to any oxide. To sum up, the amount of the material to be addedto LaAlO₃ should be equal to or smaller than (10.0+10.0) atomic %(1.6×10²² cm⁻³ in density), and more preferably, be equal to or smallerthan 2.0×10²¹ cm⁻³. Here, it is obvious that 20 atomic %, which is halfthe sum of the La amount and the Al amount, and the upper limit in anoxide (the value with which the interaction in the valence band becomesremarkably large) are the same as each other in density. This phenomenonis not coincidental, and indicates that the amount of the additionobserved immediately before the breaking of an oxide is the same as theamount of the addition with which the interaction in the valence bandbecomes remarkably large.

Further, with entropy being taken into consideration, it is preferablethat the lower limit of the amount of [divalent element] is equal to orlarger than 6.4×10¹⁹ cm⁻³, and it is more preferable that the lowerlimit of the amount of [divalent element] is equal to or larger than3.0×10²⁰ cm⁻³, as already mentioned. To sum up, in an oxide of atrivalent metal, it is preferable that the following relationship issatisfied:

6.4×10¹⁹ cm⁻³≦[divalent element]≦1.6×10²² cm⁻³

and it is more preferable that the following relationship is satisfied:

3.0×10²⁰ cm⁻³≦[divalent element]≦2.0×10²¹ cm⁻³

Now, a case where Ca is used is described. It is a known fact that, inmany materials such as Ca and Y, oxygen defects easily move and form ionconductors, and crystallization easily occurs. As a result, only a gateinsulating film having poor reliability can be obtained due to themobility of oxygen defects and trapped charges. With hydrogenintroduction, however, oxygen ions are certainly prevented from moving,and the material used as the ion conductors can be used as the gateinsulating film. Furthermore, the band offsets ΔEv and ΔEc of thematerials such as Ca and Y and the material having hydrogen introducedthereto are as good as or better than the band offsets observed in thecase of Al. As for the optimum amounts, the optimum amount of Y in HfO₂is the same as the Al amount in the above HfO₂, and the optimum amountof Ca in HfO₂ is the same as the Ba amount in the HfO₂.

Further, a case where Ba as a divalent material is added to an oxide ofa quadrivalent material is described. The addition of Ba is originallythe most expected choice. When hydrogen is introduced, however, Babecomes dissociated from oxygen defects, and there is no need to takethe oxygen defects into consideration. Thus, the characteristics aregreatly improved. Particularly, the amount of the addition is notlimited to a small amount as in conventional cases, and the same amountas in the nitrogen case can be introduced. As for the amount of oxygendefects, however, (valence difference “2”)×[divalent element], insteadof [N], is assigned into the numerical expression, if the valencedifference is 2. This means that the same amount of hydrogen as amultiple of the valence difference is required.

Accordingly, {2×[divalent element]−[H]}/2 is the amount of oxygendefects. It is preferable that the following relationship is satisfied:

{2×[divalent element]−[H]}/2≦1.0×10²¹ cm⁻³

and it is more preferable that the following relationship is satisfied:

{2×[divalent element]−[H]}/2≦3.0×10²⁰ cm⁻³

Further, with entropy being taken into consideration, it is preferablethat the lower limit of the amount of [divalent element] is equal to orlarger than 6.4×10¹⁹ cm⁻³, and it is more preferable that the lowerlimit of the amount of [divalent element] is equal to or larger than3.0×10²⁰ cm⁻³, as already mentioned.

In the divalent metal in an oxide of a quadrivalent metal, there is anelectron shortage by two electrons due to substitution. Therefore, thedivalent metal and oxygen defects form 1:1 pairs. As a result, theoptimum density of the divalent metal is half the optimum densityobtained in the case of 2:1 pairs (a “NVN” structure or an “AlVAl”structure). Accordingly, it is preferable that the optimum density ofthe divalent metal is equal to or smaller than 0.8×10²² cm⁻³, and it ismore preferable that the optimum density of the divalent metal is equalto or smaller than 1.0×10²¹ cm⁻³. This has already been mentioned in thedescription of the upper limit of the nitrogen amount.

To sum up, in an oxide of a quadrivalent metal, it is preferable thatthe following relationship is satisfied:

6.4×10¹⁹ cm⁻³≦[divalent element]≦0.8×10²² cm⁻³

and it is more preferable that the following relationship is satisfied:

3.0×10²⁰ cm⁻³≦[divalent element]≦1.0×10²¹ cm⁻³

The amount of addition is basically determined by the valence differencebetween the parent metal and the metal to be added. The optimum amountis 2[Ba]=[H]. It is preferable that {2[Ba]−[H]}/2 is equal to or smallerthan 8.33 atomic %, and it is more preferable that {2[Ba]−[H]}/2 isequal to or smaller than 7.4 atomic %. Further, the conditions,0<[Ba]<16.7 atomic % and 0<[H]<33.4 atomic %, are the same as those inthe case of Al.

As described above, when a material having lower valence than thevalence of the parent metal is introduced, oxygen defects are formed,and hydrogen fills up the oxygen defects. The same applies to many kindsof materials.

Optimum examples of metal elements having quadrivalent parent metalsinclude Hf, Zr, and Ti, and at least one of the elements should be used.In this case, the material to be added is a trivalent metal element or adivalent metal element. Examples of trivalent metal elements include Laand Al. Those trivalent metal elements originally tend to have phaseseparation due to the ion radius, but the phase separation is causedbecause the oxide is stable. As hydrogen is introduced, the possibilityof phase separation becomes zero. With the ion radius and stabilitybeing taken into consideration, La and Al are most effective.

Also, the group of elements Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,Ho, Er, Tm, Yb, and Lu are also effective. Those are the elements thathave the possibility to form ion conductors. However, with hydrogenbeing introduced, there are no possibilities that those elements formion conductors. This embodiment has proved for the first time that thoseelements are normally unsuitable as insulating films, but can exhibitexcellent characteristics as insulating films after hydrogen isintroduced. Materials having any of those elements introduced theretohave very high structural stability, and are very useful accordingly.

Optimum examples of divalent metal elements include Mg, Sr, and Ba.Those elements have the problem of becoming dissociated from oxygendefects, and therefore, can be introduced only with low concentration.However, those problems disappear once hydrogen is introduced. Also, Cacan be used. Ca is a material that might form ion conductors, but has nopossibilities to form ion conductors once hydrogen is introduced.Materials having any of those elements introduced thereto have very highstructural stability, and are very useful accordingly.

Optimum examples of trivalent metal elements as parent metals includeLa, Al, and Y, and at least one of those elements should be used. Forexample, LaAlO₃, YAlO₃, La₂O₃, Al₂O₃, Y₂O₃, and the likes are effective,in terms of stability and dielectric characteristics. The material to beadded to an oxide having any of those trivalent parent metals may be adivalent element (Ba, Sr, Ca, or Mg).

Also, silicates (such as HfSiO₄ and LaAlSiO₅) may be used as parentmetal oxides. In a silicate, an added material such as nitrogen mightexist only on the silicon side. This is probably because higherstability is maintained when N exists locally in SiO₂ rather than when Nexits in a parent material such as HfO₂ or LaAlO₃. As hydrogen isintroduced, a hydrogen structure is formed in HfO₂ or LaAlO₃, and highstability is achieved. Accordingly, nitrogen moves toward the HfO₂ orLaAlO₃ side, and the above effect is achieved. In this manner, a largeeffect is achieved even in a silicate.

Next, the difference between the H addition employed in this embodimentand the FGA process is described.

In the LSI process, FGA (H₂ annealing) is often used. The H in aninsulating film is to recover a very small amount of defects caused inthe initial stage of the film formation, with the use of a very smallamount of hydrogen. More specifically, the hydrogen fills up unstableoxygen defects Vo existing independently of other parts, and releasesexcess oxygen to the outside. However, the hydrogen does not fill upoxygen defects in a stable “NVoN” structures or “BaVo” structure.Rather, this process is regarded as the process of producing thosestable “NVoN” and “BaVo” structures (JP-A 2007-273587 (KOKAI)). Unlikethe process in accordance with this embodiment, FGA (H₂ annealing) isnot a process in which nitrogen or a low-valence metal element isintroduced, and an optimum amount of hydrogen excited in an atomic stateis introduced by virtue of stabilization achieved by the movement ofelectrons caused by charge compensation. Therefore, the amount ofhydrogen introduced into the film is also very small. In thisembodiment, on the other hand, an interaction is caused between oxygendefects formed through the introduction of nitrogen or a low-valencemetal element and hydrogen excited in an atomic state, and a stablestructure is established. In this manner, this embodiment provides anovel film that does not cause decreases in the band offsets ΔEc and ΔEvdue to the introduction of nitrogen or a low-valence metal element. Torealize the structure of this embodiment, H excited in an atomic stateis preferable to H₂ in a molecular state.

In the process of manufacturing a semiconductor device, the surface of aSi substrate is sometimes terminated with H. In that case, hydrogenhaving area density in the order of 10¹⁴ cm⁻² exists in the interfaceregion. Normally, the hydrogen in the interface region is removed fromthe termination during the film formation, and is discharged from thefilm forming apparatus. Accordingly, the amount of hydrogen remaining inthe insulating film should be almost zero, and be in the order of 10¹⁸cm⁻³ or less in density. In a regular process, hydrogen is released tothe outside through a heat treatment, and the amount of hydrogen in theinsulating film is reduced as much as possible. After that, H isabsorbed at the interface between the substrate and the insulating filmafter the H₂ annealing, but there are little hydrogen existing in thefilm.

As described so far, in accordance with this embodiment, oxygen defectscan be restricted as much as possible, and the leakage current can bereduced. Thus, an insulating film with high reliability can be obtained.

Next, the embodiment is described in greater detail through thefollowing examples.

EXAMPLE 1

FIG. 19 illustrates an n-type MISFET in accordance with Example 1. TheMISFET of Example 1 has the oxide film of the above embodiment as a gateinsulating film.

In the MISFET of Example 1, an n-type source and drain regions 22 a and22 b are formed at a distance from each other on a p-type Si substrate21, and a gate insulating film 24 is formed on a portion of the siliconsubstrate 21. The portion is to be a channel region 23 between thesource region 22 a and the drain region 22 b. A gate electrode 25 isformed on the gate insulating film 24.

Next, the procedures for manufacturing the MISFET of Example 1 aredescribed. First, the clean surface of the Si substrate 21 having a(001)-plane as the principal surface is revealed. In this procedure, aregular HF (hydrofluoric acid) treatment is carried out, and anextremely thin oxide film SiO₂ is formed through room-temperature ozoneoxidation. Surface protection is then conducted.

The Si substrate 21 is then transported to a sputtering device, and theimpurities in the outermost surface evaporate in a ultrahigh vacuum at250° C. The temperature is then increased to 880° C., so that the oxidefilm SiO₂ in the surface evaporates. At this point, the clean surfaceappears, and the surface has a 2×1 structure, as can be observed throughreflection high-energy electron diffraction (RHEED).

The amorphous HfO₂ film as the gate insulating film 24 is then formed bysputtering at a low temperature of 300° C. The film thickness of theHfO₂ film is 4 nm. Here, the oxygen partial pressure is set at zerosince the initial stage of the sputtering film formation, and the filmformation is performed in a reduced atmosphere of an atmosphere havingplasma nitrogen and plasma hydrogen introduced thereto. Alternatively,plasma nitrogen and plasma hydrogen may not be introduced during theHfO₂ film formation, and plasma nitrogen may be introduced after theHfO₂ film is formed. Plasma hydrogen may be then introduced. In such acase, however, oxygen is released from the HfO₂ film. Therefore, theplasma nitrogen and hydrogen introduction should be performed while theHfO₂ film is not covered with an electrode or the like, so as to preventoxygen from entering the interface with the silicon substrate.

With this arrangement, the amount of nitrogen to be introduced and theamount of hydrogen to be introduced can be controlled by adjusting theamount of plasma, the time of exposure to plasma, and the plasmatemperature. In this example, films are formed, with the nitrogen amountbeing varied from 0.1 atomic % (9.6×10¹⁹ cm⁻³ in density), to 2.0 atomic% (1.9×10²¹ cm⁻³ in density), and to 10.0 atomic % (9.6×10²¹ cm⁻³ indensity). The amount of hydrogen to be introduced also varies with thetime of exposure to plasma hydrogen. If the time of exposure to plasmahydrogen is too short, oxygen defects are dispersed in the film, andresult in a leakage current. Since electrons are trapped by oxygendefects when hydrogen is introduced to a certain level, the film isnegatively charged. The amount of oxygen defects at this point can bedetermined by carrying out STS measurement on the film or observing thethreshold value variation in a MOS structure. If the amount of oxygendefects becomes less than 1.1 atomic % (1.0×10²¹ cm⁻³ in density), theleakage current is reduced to an allowable level. (When the amount ofoxygen defects is 0.31 atomic % (3.0×10²⁰ cm⁻³ in density), the leakagecurrent is reduced to 10 times as much as the saturation leakagecurrent.) If the amount of oxygen defects becomes less than 0.31 atomic%, almost no leakage current flows. The amount of oxygen defects may bereduced further. However, the leakage characteristics hardly change ifthe amount of oxygen defects becomes less than 0.31 atomic % anddecreases even further. In other words, the leakage current has reachedthe saturation point, and reflects the performance of the HfO₂ film.However, if electrons are accumulated at oxygen defects, a thresholdvalue shift in the MOS structure is observed. Accordingly, the amount ofoxygen defects can be even more precisely measured by checking whetherthere is a threshold value shift. By introducing a sufficient amount ofhydrogen atoms, film formation is performed while the amount of oxygendefects is further reduced. Where the ratio between the nitrogen amountand the hydrogen amount is 1:1, the most stable state is achieved, andextra hydrogen can be released to the outside. Accordingly, the amountof oxygen defects can become zero in principle. In such a case, athreshold value shift hardly occurs in the MOS structure that isobserved for a threshold value shift, as will be described later.

After that, 30-second rapid thermal annealing (RTA) is performed in avacuum at 900° C. A polysilicon film to be the gate electrode is thenformed, and processing is performed to turn the polysilicon film intothe gate electrode 25. After sidewalls are formed (not shown), electrodeion implantation (P ions) is performed, followed by spike annealing at1050° C. and H₂ sintering, in a case where ions are injected into thesource and drain regions while polysilicon is used for an electrode. Ina case where a metal electrode is used, a metal film is formed after thesource and drain are activated. The results of the secondary ion massspectrometer (SIMS) analysis conducted on the distributions of thehydrogen concentration and the nitrogen concentration in the gateinsulating film 24 where the nitrogen amount is 2.0 atomic % arerepresented by the graphs shown in FIG. 10. In the gate insulating film24, the hydrogen concentration distribution and the nitrogenconcentration distribution overlap with each other, and may be regardedas the same as each other, in view of the precision of the SIMSanalysis. Here, a large amount of hydrogen exists in the interfacebetween the Si substrate 21 and the insulating film 24. This is becausethe dangling bonds in the surface of the substrate 21 are terminated.This indicates that hydrogen can be located in the vicinity of nitrogenat the ratio of 1:1 inside the gate insulating film 24 formed by thefilm forming method of this example. As can be seen from the SIMSanalysis results, better characteristics can be achieved when a largeramount of added material is distributed on the electrode side. Nitrogenand hydrogen are electrically charged in the bulk, and the charge amountbecomes zero when N and H form pairs. The charge amounts of bothmaterials are hardly visible at a location far away from the channelregion 23, but positively-charged and negatively-charged distributionscan be seen at a location close to the channel region 23. Therefore, thedistribution of N—H pairs should be minimized in the portion equivalentto an insulating film layer in the vicinity of the channel region 23 orin a region of approximately 2.5 angstroms in the vicinity of thechannel region 23. An insulating film that has fewer N—H pairs in theinterface with the silicon substrate can be readily realized bycontrolling the procedures of nitridation and hydrogenation. Forexample, the amounts of excited nitrogen and excited hydrogen may be setat zero in the initial stage of the film formation, and be graduallyincreased. Also, if plasma nitridation and plasma hydrogenation areperformed after the formation of the HfO₂ film, a film that has highconcentration in the upper film portion and low concentration in thevicinity of the substrate can be readily realized. As shown in FIG. 10,a mobility comparison is made between a MOSFET that has high N and Hconcentration in the insulating film 24 but low N and H concentration inthe vicinity of the silicon substrate, and a MOSFET that has N and Hintroduced uniformly into the entire insulating film and has N—H pairsdistributed in large number even in the interface between the Sisubstrate and the insulating film. According to the comparison, thedifference in mobility between the two MOSFETs is approximately 20%.Therefore, a film that has fewer N-H pairs in the vicinity of theinterface with the Si substrate as in Example 1 is considered to bebetter.

In Example 1, the film formation is performed by a sputtering technique,but the same result can be achieved by MBE, CVD, ALD, or the like.

For n-type MISFETs formed in the above described manner, acharacteristic comparison is also made between an n-type MISFET that hashydrogen added thereto and an n-type MISFET that has no hydrogen addedthereto. In both MISFETs, the gate insulating film 24 is a thin gateinsulating film of 0.65 nm in film thickness (EOT) converted into thefilm thickness of a SiO₂ film.

The leakage current generated when a large electric field of 5 MV/cm isinduced is then measured. The leakage current in the MISFET having nohydrogen added thereto is 1.0 A/cm² or less, but the leakage current inthe MISFET having hydrogen added thereto is much lower, being 0.0005A/cm². The gate film of the MISFET having no hydrogen added thereto hasmicrocrystals precipitated, but the film of the MISFET having hydrogenadded thereto maintains an amorphous state. In the case of the MISFEThaving hydrogen added thereto, crystallization is caused if the nitrogenamount and the hydrogen amount are as small as approximately 0.1 atomic%, and the leakage current is increased. In the MISFET having the smallamounts of nitrogen and hydrogen added thereto, it has become clear thatcrystallization is not caused if the PDA procedure is carried out at alow temperature of 600° C. for 30 seconds, the H₂ sintering is performedat a low temperature of 450° C., and the spike annealing is performed ina vacuum at 1050° C.

A comparative experiment is also conducted on HfON that is an often-usedHfO₂ film having a large amount of nitrogen added thereto. The nitrogenamount is set at approximately 24 atomic %, which is twice the nitrogenamount in the above example or more. At this point, the originalamorphous structure is maintained. However, the leakage current measuredwhen a large electric field of 5 MV/mc is induced is approximately 0.1A/cm² in the HfO₂ film having only N added thereto. This is only 10% ofthe leakage current observed in a HfO₂ film having no N added thereto,because the amorphous structure is maintained. As described above, ithas become clear that the leakage current in the HfO₂ film after thehydrogen addition is much lower than the leakage current prior to thehydrogen addition. With only nitrogen being added to a regular HfONfilm, the band offset ΔEc on the conduction band side decreases byalmost 0.5 eV. This is the principal reason that the leakage currentcharacteristics are not sufficiently improved. In Example 1, on theother hand, hydrogen as well as nitrogen is added, and the band offsetΔEc does not decrease. Accordingly, HfO₂ can exhibit its inherentcharacteristics.

As for the time-dependent changes observed while voltages are beingapplied, the HfO₂ film having neither nitrogen nor hydrogen addedthereto breaks down within a few hours, and the HfO₂ film havingnitrogen (24 atomic %) added thereto breaks down in almost eight hours.On the other hand, the HfO₂ film having 2.0 atomic % of nitrogen and 2.0atomic % of hydrogen added thereto does not break down even afterseveral days.

In the MISFET that does not have nitrogen and hydrogen introduced intothe gate insulating film, the threshold voltage shifts with time in aremarkable manner, and a shift of 100 mV or larger is observed inapproximately one hour. In the MISFET having only nitrogen introducedinto the gate insulating film, a shift of 100 mV is observed in eighthours. In the MISFET having only nitrogen added to the gate insulatingfilm, the shift is caused because the fixation of the oxygen defects isweak. In the MISFET having nitrogen and hydrogen introduced into thegate insulating film, only a shift of 10 mV is observed even afterseveral days, and there is hardly a change thereafter. This is becausethere are no structural changes and no trapped charges that cause oxygendefects as the insulating film characteristics.

Likewise, p-type MISFETs are examined. There is the problem ofcrystallization in HfO₂ alone, and there is a band offset decrease in ap-type MISFET having nitrogen added thereto. However, in an insulatingfilm having 2.0 atomic % of nitrogen and 2.0 atomic % of hydrogen addedthereto, a decrease of the band offset is prevented. As a result, ap-type MISFET with excellent leakage characteristics is obtained.Further, as for long-term reliability, the same effects as those of ann-type MISFET are achieved. In a case where 10 atomic % of nitrogen and10 atomic % of hydrogen are introduced, the leakage in the p-type MISFETbecomes approximately ten times larger.

The effects of the addition of both hydrogen and nitrogen into a gateinsulating film greatly contribute to improvement of the characteristicsof the insulating film. The C-V characteristics (capacitance-voltagecharacteristics) exhibit an excellent rise, and draw a steep curve.Meanwhile, the hydrogen existing in the interface with the Si substratecauses a shift of the rising point of the C-V characteristics. Whencombined with the hydrogen adding process, the two aspects can becombined with each other. The shift of the C-V characteristics caused bythe hydrogen in the interface has a problem that the rise of the C-Vcharacteristics becomes poor. It is considered that the deformation ofthe C-V characteristics affects the operation of the MISFET, anddegrades the current driving performance. As shown in this example, therise of the C-V characteristics is improved if hydrogen and nitrogen areintroduced into the insulating film. With those aspects being combined,a p-type MISFET that has a shift of the C-V characteristics because ofthe hydrogen in the channel and also has a very good rise of the C-Vcharacteristics can be obtained.

The effects of the improvement of the film characteristics described sofar are that oxygen defects disappear by virtue of hydrogen, the bandgapis not narrowed, and there is not a level appearing in the gap. Inaccordance with this example, the characteristics and reliability of thegate insulating film are greatly improved.

In this example, HfONH is taken as an example. However, an excellentgate insulating film that has no oxygen defects, no narrowing of thebandgap, and no levels in the gap can be obtained by using HfO₂ having Hand a trivalent material such as La or Al added thereto, ZrO₂ having Hand a divalent material such as Ca or Mg added thereto, LaAlO₃ having Hand a divalent material such as Ba added thereto, or the like.

As described above, in accordance with this example, oxygen defects canbe restricted as much as possible, and the leakage current can bereduced. Accordingly, a gate insulating film with high reliability and aMISFET including the gate insulating film can be obtained.

EXAMPLE 2

FIG. 20 shows a MIM (metal insulator metal) capacitor in accordance withExample 2. The MIM capacitor of Example 2 includes: a buffer film 32that is made of TlAlN or the like and is formed on a substrate 31; anelectrode 33 that is made of Pt and is formed on the buffer film 32; acapacitor insulating film 34 that is formed on the electrode 33; and anelectrode 35 that is made of Pt and is formed on the capacitorinsulating film 34. The capacitor insulating film 34 is formed with theHfO₂ film having La added thereto as described in the above embodiment.

Next, the procedures for manufacturing the MIM capacitor of Example 2are described. First, through the same procedure as that of Example 1,the clean surface of the substrate 31 having a (001)-plane as itsprincipal surface is caused to appear.

After the buffer film 32 and the electrode 33 are formed in this order,a HfO₂ film to be the capacitor insulating film 34 is formed on theelectrode 33 by performing sputtering at a high temperature of 800° C.The film thickness of the HfO₂ film is 10 nm. The oxygen partialpressure is set at zero since the initial stage of the sputtering filmformation.

When the HfO₂ film is formed, a target of La₂Hf₂O₇ is introduced, andsimultaneous sputtering is performed. The oxygen partial pressure is setat zero since the initial stage of the sputtering film formation, andthe film formation is performed in a reduced atmosphere of an atmospherehaving plasma hydrogen (or excited hydrogen) introduced thereto. Here,the amount of La to be added is very large, and is approximately 2.0atomic % (1.9×10²¹ cm⁻³ in density). The amount of La to be added iscontrolled by adjusting the voltage to be applied to the target. In thisexample, the film formation is performed by a sputtering technique, butthe same result can be achieved by MBE, CVD, ALD, or the like. Afterthat, 30-second RTA is performed at 900° C.

A Pt film to be the electrode 35 is then formed by sputtering. SIMSanalysis is conducted on the distributions of the hydrogen concentrationand the La concentration in the capacitor insulating film 34. In thecapacitor insulating film 34, the hydrogen concentration distributionand the La concentration distribution overlap with each other, and maybe regarded as the same as each other, in view of the precision of theSIMS analysis. This indicates that hydrogen can be located in thevicinity of La at the ratio of 1:1, depending on the film formationmethod in this example.

MIM capacitors are produced in the above manner, and the characteristicsof a capacitor having no hydrogen added to the capacitor insulating filmand the characteristics of a capacitor having hydrogen added to thecapacitor insulating film are examined. First, in each of thecapacitors, the capacitor insulating film 34 is a thin gate insulatingfilm of 0.45 nm in film thickness (EOT (Equivalent Oxide Thickness))converted into the thickness of SiO₂.

The leakage current generated when a large electric field of 5 MV/cm isinduced is then measured. The leakage current in the capacitor having nohydrogen added thereto is 1.0 A/cm² or less, but the leakage current inthe capacitor having hydrogen added thereto is much lower, being 0.005A/cm². There are a large amount of oxygen defects in the HfO₂ having Laadded thereto in the capacitor having no hydrogen added thereto. Sinceelectrons can easily enter and leave oxygen defects, the oxygen defectsare considered to be the cause of an increase in leakage current.However, as hydrogen enters the oxygen defects, the cause of the leakagecurrent increase is eliminated.

As for the time-dependent changes observed while voltages are beingapplied, the capacitor having no hydrogen introduced thereto breaks downwithin a few hours, but the capacitor having hydrogen introduced theretodoes not break down even after several days.

In the capacitor having no hydrogen introduced thereto, charges areaccumulated with time, and the results of an examination conducted onthe capacitance-voltage (C-V) characteristics indicate that thehysteresis is larger in the increasing and decreasing direction of theapplied voltage. In the film having hydrogen introduced thereto, on theother hand, the hysteresis is restricted to 10 mV or less.

The effects of the improvement of the film characteristics described sofar are that oxygen defects disappear by virtue of hydrogen, the bandgapis not narrowed, and there is not a level appearing in the gap. Inaccordance with this example, the characteristics and reliability of thecapacitor insulating film are greatly improved.

In this example, HfO₂ having La and H added thereto is taken as anexample. However, an excellent capacitor insulating film that has nooxygen defects, no narrowing of the bandgap, and no levels in the gapcan be obtained by using HfO₂ having N and H added thereto, ZrO₂ havingH and a divalent material such as Ca or Mg added thereto, LaAlO₃ havingH and a divalent material such as Ba added thereto, or the like.

As described above, in accordance with this example, oxygen defects canbe restricted as much as possible, and the leakage current can bereduced. Accordingly, a capacitor insulating film with high reliabilityand a MIM capacitor including the capacitor insulating film can beobtained.

EXAMPLE 3

FIG. 21 shows a semiconductor device in accordance with Example 3. Thesemiconductor device of Example 3 is a flash-memory cell transistor, andincludes: a source region 42 a and a drain region 42 b that are formedat a distance from each other on a Si substrate 41; a tunnel insulatingfilm 44 that is formed on the portion of the Si substrate to be achannel region 43 between the source region 42 a and the drain region 42b; a floating gate electrode 45 that is formed on the tunnel insulatingfilm 44; an interelectrode insulating film 46 that is formed on thefloating electrode 45; and a control gate electrode 47 that is formed onthe interelectrode insulating film 46. The tunnel insulating film 44 isformed with amorphous SiON, for example. The electrodes 45 and 47 areformed with polysilicon doped with phosphorus (P). The interelectrodeinsulating film 46 is formed with one of the oxides according to theabove embodiment, as will be described later in detail.

Next, the procedures for manufacturing the memory cells of Example 3 aredescribed. First, through the same procedure as that of Example 1, theclean surface of the substrate 41 having a (001)-plane as its principalsurface is caused to appear.

The tunnel insulating film 44 formed with SiON, the floating electrode45 formed with P-doped polysilicon, and the interelectrode insulatingfilm 46 formed with H-added HfAlO are then formed in this order. TheHfAlO film is formed by performing sputtering at a high temperature of800° C. The film thickness of the HfAlO film is 15 nm. The oxygenpartial pressure is set at zero since the initial stage of thesputtering film formation, and the film formation is performed in areduced atmosphere of an atmosphere having plasma hydrogen (or excitedhydrogen) introduced thereto. In the sputtering film formation, twotargets, an Al₂O₃ target and a HfO₂ target, are used. After the filmformation, the amount of Al in the HfAlO film is 1.8 atomic % (1.7×10²¹cm⁻³ in density). In this example, the film formation is performed by asputtering technique, but the same result can be achieved by MBE, CVD,ALD, or the like. After that, 30-second RTA is performed at 900° C. AP-doped polysilicon film to be the control gate electrode 47 is thenformed on the interelectrode insulating film 46.

SIMS analysis is conducted on the distributions of the hydrogenconcentration and the Al concentration in the interelectrode insulatingfilm 44 formed with a HfO₂ film having H and Al added thereto. In theinterelectrode insulating film 44, the hydrogen concentrationdistribution and the Al concentration distribution overlap with eachother, and may be regarded as the same as each other, in view of theprecision of the SIMS analysis. This indicates that hydrogen can belocated in the vicinity of Al at the ratio of 1:1, depending on the filmformation method in this example.

After that, ion implantation or the like is performed to form the sourceregion 42 a and the source region 42 b on the surface of the substrate41, with the channel region 43 being interposed between the sourceregion 42 a and the drain region 42 b . In this manner, a flash-memorycell transistor is formed.

Memory cells are produced in the above manner, and the characteristicsof a memory cell having hydrogen added to the interelectrode insulatingfilm 46 and the characteristics of a memory cell having no hydrogenadded to the interelectrode insulating film 46 are examined. First, ineach of the memory cells, the interelectrode insulating film 46 is athin insulating film of 2.5 nm in film thickness (EOT) converted intothe film thickness of a SiO₂ film.

The leakage current generated when a large electric field of 5 MV/cm isinduced is then measured. The leakage current in the memory cell havingno hydrogen added thereto is approximately 0.1 A/cm², but the leakagecurrent in the memory cell having hydrogen added thereto is much lower,being 0.0001 A/cm². The interelectrode insulating film of the memorycell having no hydrogen added thereto is a HfO₂ film having Al addedthereto, and there are a large amount of oxygen defects existing in theHfO₂ film. Since electrons can easily enter and leave oxygen defects,the oxygen defects are considered to be the cause of an increase inleakage current. In the interelectrode insulating film of the memorycell of this example, however, the cause of the leakage current increaseis eliminated, as hydrogen enters the oxygen defects.

As for the time-dependent changes observed while voltages are beingapplied, the memory cell having no hydrogen introduced thereto breaksdown within a few hours, but the memory cell having hydrogen introducedthereto does not break down even after several days.

In the interelectrode insulating film having no hydrogen introducedthereto, charges are accumulated with time, and the results of anexamination conducted on the capacitance-voltage (C-V) characteristicsindicate that the hysteresis is larger in the increasing and decreasingdirection of the applied voltage. In the interelectrode insulating filmhaving hydrogen introduced thereto, on the other hand, the hysteresis isrestricted to 10 mV or less.

In the memory cell having hydrogen introduced into the interelectrodeinsulating film as in this example, only several percents of accumulatedcharges disappear even after several days have passed. In the memorycell having no hydrogen introduced into the interelectrode insulatingfilm, on the other hand, the accumulated charges are rapidly released tothe outside, and disappear within several hours. This is because thereare many oxygen defects, and a leakage current easily flows through theoxygen defects. In conventional cases, it is necessary to prevent theleakage current by forming a multilayer film such as anAl₂O₃/HfAlO/Al₂O₃ film, though the film thickness becomes larger.However, in view of the charge accumulation, it has become apparent thata multilayer film structure does not need to be formed if an appropriateamount of hydrogen is introduced as in this example.

The effects of the improvement of the insulating film characteristicsdescribed so far are that oxygen defects disappear by virtue ofhydrogen, the bandgap is not narrowed, and there is not a levelappearing in the gap. In accordance with this example, thecharacteristics and reliability of the interelectrode insulating filmare greatly improved.

In this example, HfO₂ having Al and H added thereto is taken as anexample. However, an excellent interelectrode insulating film that hasno oxygen defects, no narrowing of the bandgap, and no levels in the gapcan be obtained by using HfO₂ having N and H added thereto, ZrO₂ havingH and a divalent material such as Ca added thereto, LaAlO₃ having H anda divalent material such as Ba added thereto, or the like.

As described above, in accordance with this example, oxygen defects canbe restricted as much as possible, and the leakage current can bereduced. Accordingly, an interelectrode insulating film with highreliability and a memory cell transistor including the interelectrodeinsulating film can be obtained.

In this example, the interelectrode insulating film is formed with theinsulating film in accordance with the embodiment. However, since theinsulating film in accordance with the embodiment can also be used as atunnel insulating film, the interelectrode insulating film and thetunnel insulating film of this example may be both formed with theinsulating film in accordance with the embodiment.

EXAMPLE 4

FIG. 22 shows a semiconductor device in accordance with Example 4. Thesemiconductor device of this example is the same as the memory celltransistor of Example 3 shown in FIG. 21, except that the floating gateelectrode 45 is replaced with a charge trapping film 45A formed with asilicon nitride film, for example. The semiconductor device of thisexample is a charge-trapping memory cell transistor. Although theinterelectrode insulating film 46 of Example 3 is referred to as a blockinsulating film 46 in Example 4, the block insulating film 46 is formedwith the same HfO₂ film having Al and H added thereto as theinterelectrode insulating film 46 of Example 3.

In Example 4, a HfO₂ film having Al and H added thereto is used as theblock insulating film 46. However, an excellent block insulating filmthat has no oxygen defects, no narrowing of the bandgap, and no levelsin the gap can be obtained by using HfO₂ having N and H added thereto,ZrO₂ having H and a divalent material such as Ca or Mg added thereto,LaAlO₃ having H and a divalent material such as Ba added thereto, or thelike.

As described above, in accordance with this example, oxygen defects canbe restricted as much as possible, and the leakage current can bereduced. Accordingly, a block insulating film with high reliability anda memory cell transistor including the block insulating film can beobtained.

In this example, the block insulating film is formed with the insulatingfilm in accordance with the embodiment. However, since the insulatingfilm in accordance with the embodiment can also be used as a tunnelinsulating film or a charge trapping film, at least one of the tunnelinsulating film, the charge trapping film, and the block insulating filmof this example may be formed with the insulating film in accordancewith the embodiment.

The insulating film in accordance with the embodiment has a metal oxideas its parent material. As hydrogen is introduced into the insulatingfilm, the amount of oxygen defects that can move in the insulating filmis greatly reduced. However, when hydrogen is introduced, only anappropriate amount of nitrogen or a metal material with lower valencethan the parent metal of the insulating film also needs to beintroduced.

This embodiment is characterized in that, by adding N, a low-valencematerial such as Al, La, Y, Sc, Ba, Sr, Ca, or Mg, or a lanthanum seriesmaterial, the number of oxygen defects in the oxide is increased, andthe oxygen defects are tightly fixed with hydrogen to lose the mobility.Oxygen defects induce various kinds of deteriorations in many oxideshaving high dielectric constants. However, by introducing an appropriateamount of hydrogen, the film degradation to be caused by oxygen defectscan be prevented. However, if only hydrogen is introduced, a chargecenter or the like is induced. Therefore, an appropriate amount ofanother material as well as hydrogen is introduced. In this manner, itbecomes possible to eliminate the problems that are caused if only oneof the materials is introduced.

As a result, the following effects are achieved: (1) an amorphousstructure can be maintained at a high temperature; (2) since there is nonarrowing of the bandgap and there is not a level appearing in the gap,leakage current is greatly improved; (3) much higher reliability isobtained, as oxygen defects disappear, and hydrogen is fixed at latticespoints; (4) internal fixed charges or fixed polarization are not caused,as the entire system is stabilized through charge compensation; (5)there is no breakdown due to injected charges, since there is not alevel at which charges are injected; (6) an added material that normallyforms ion conductors can be used as a high-performance insulating film,since an appropriate amount of hydrogen is introduced; and (7) an addedmaterial that might cause phase separation can be used as ahigh-performance insulating film, since an appropriate amount ofhydrogen is introduced.

As can be seen from the above described embodiment and examples, aninsulating film in accordance with an embodiment contains a first metalelement, oxygen, hydrogen, and one element of a second metal element andnitrogen. This insulating film satisfies the following relationship:

{k×[X]−[H]}/2≦1.0×10²¹ cm⁻³

where [X] represents the amount of the one element, [H] represents thehydrogen amount, and k represents the difference in valence between thefirst metal element and the second metal element or the difference invalence between oxygen and nitrogen.

In a case where the one element is nitrogen, the relationship, [X]=[N],is satisfied, where [N] represents the nitrogen amount, and k representsthe difference in valence between oxygen and nitrogen, which is 1.

In a case where the one element is the second metal element, the firstmetal element is a quadrivalent metal, and the second metal element is atrivalent metal, the relationship, [X]=[III metal], is satisfied, where[III metal] represents the amount of the trivalent metal, and k is 1.

In a case where the one element is the second metal element, the firstmetal element is a quadrivalent metal, and the second metal element is adivalent metal, the relationship, [X]=[II metal], is satisfied, where[II metal] represents the amount of the divalent metal, and k is 2.

In a case where the one element is the second metal element, the firstmetal element is a trivalent metal, and the second metal element is adivalent metal, the relationship, [X]=[II metal], is satisfied, and k is1.

The amount [X] of the one element and the hydrogen amount [H] mightsatisfy the following relationship:

{k×[X]−[H]}/2≦3.0×10²⁰ cm⁻³

The amount [X] of the one element might satisfy the followingrelationship:

6.4×10¹⁹ cm⁻³≦[X]≦1.6×10²² cm⁻³/k

The amount [X] of the one element might satisfy the followingrelationship:

3.0×10²⁰ cm⁻³≦[X]≦2.0×10²¹ cm⁻³/k

The insulating film may be an amorphous film.

The insulating film may be a silicate.

In the insulating film, the one element may be nitrogen, k is 1, and therelationship, k×[X]=1×[N], is satisfied, where the nitrogen amount isequal to or larger than the hydrogen amount, and the hydrogen atoms arecoupled to the nitrogen atoms through one atom of the first metalelement.

In the insulating film, the one element may be the second metal element,the first metal element may be a quadrivalent metal element, and thesecond metal element may be a trivalent metal element, k is 1, and therelationship, k×[X]=1×[III metal], is satisfied, where the amount of thetrivalent metal element is equal to or larger than the hydrogen amount,and the trivalent metal element is located adjacent to the hydrogen.

In the insulating film, the one element may be the second metal element,the first metal element may be a quadrivalent metal element, and thesecond metal element may be a trivalent metal element, k is 1, and therelationship, k×[X]=1×[III metal], is satisfied, where the quadrivalentmetal element contains one metal element selected from the group of Hf,Zr, and Ti, and the trivalent metal element contains one metal elementselected from the group of Al, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb, and Lu.

In the insulating film, the one element may be the second metal element,the first metal element may contain a quadrivalent metal element, andthe second metal element may contain a divalent metal element, k is 2,and the relationship, k×[X]=2×[II metal], is satisfied, where 2×[IImetal], which is twice the amount of the divalent metal element, isequal to or larger than the hydrogen amount, and the hydrogen is coupledto the divalent metal element.

In the insulating film, the one element may be the second metal element,the first metal element may contain a quadrivalent metal element, andthe second metal element may contain a divalent metal element, k is 2,and the relationship, k=[X]=2×[II metal], is satisfied, where thequadrivalent metal element contains one metal element selected from thegroup of Hf, Zr, and Ti, and the divalent metal element contains onemetal element selected from the group of Mg, Ca, Sr, and Ba.

In the insulating film, the one element may be the second metal element,the first metal element may contain a trivalent metal element, and thesecond metal element may contain a divalent metal element, k is 1, andthe relationship, k×[X]=1×[II metal], is satisfied, where the amount ofthe divalent metal element is equal to or larger than the hydrogenamount, and the divalent metal element is located adjacent to thehydrogen.

In the insulating film, the one element may be the second metal element,the first metal element may contain a trivalent metal element, and thesecond metal element may contain a divalent metal element, k is 1, andthe relationship, k×[X]=1×[II metal], is satisfied, where the trivalentmetal element contains one element selected from the group of Al, Sc, Y,La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and thedivalent metal element contains one element selected from the group ofMg, Ca, Sr, and Ba.

It is obvious to those skilled in the art that various changes andmodifications may be made to the above embodiments and examples withoutdeparting from the spirit of the invention, and those changes andmodifications should be considered to be within the scope of theinvention.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcepts as defined by the appended claims and their equivalents.

1. An insulating film comprising an amorphous oxide dielectric filmcontaining a metal, hydrogen, and nitrogen, the nitrogen amount [N] andthe hydrogen amount [H] in the oxide dielectric film satisfying thefollowing relationship:{[N]−[H]}/2≦1.0×10²¹ cm⁻³.
 2. The insulating film according to claim 1,wherein the nitrogen amount [N] and the hydrogen amount [H] in the oxidedielectric film satisfy the following relationship:{[N]−[H]}/2≦3.0×10²⁰ cm⁻³.
 3. The insulating film according to claim 1,wherein the nitrogen amount [N] and the hydrogen amount [H] in the oxidedielectric film are equal to each other.
 4. The insulating filmaccording to claim 1, wherein: the nitrogen amount [N] in the oxidedielectric film satisfies the following relationship:6.4×10¹⁹ cm⁻³≦[N]≦1.6×10²² cm⁻³; and the hydrogen amount [H] in theoxide dielectric film satisfies the following relationship:6.4×10¹⁹ cm⁻³≦[H]≦1.6×10²² cm⁻³.
 5. The insulating film according toclaim 1, wherein: the nitrogen amount [N] in the oxide dielectric filmsatisfies the following relationship:3.0×10²⁰ cm⁻³≦[N]≦2.0×10²¹ cm⁻³; and the hydrogen amount [H] in theoxide dielectric film satisfies the following relationship:3.0×10²⁰ cm⁻³≦[H]≦2.0×10²¹ cm⁻³.
 6. The insulating film according toclaim 1, wherein: the nitrogen amount in the oxide dielectric film isequal to or larger than the hydrogen amount; and each hydrogen atom iscoupled with a nitrogen atom through one atom of the metal.
 7. Aninsulating film comprising an amorphous oxide dielectric film containinga quadrivalent metal, a trivalent metal, and hydrogen, the trivalentmetal amount [III metal] and the hydrogen amount [H] in the oxidedielectric film satisfying the following relationship:{[III metal]−[H]}/2≦1.0×10²¹ cm⁻³.
 8. The insulating film according toclaim 7, wherein the trivalent metal amount [III metal] and the hydrogenamount [H] in the oxide dielectric film satisfy the followingrelationship:{[III metal]−[H]}/2≦3.0×10²⁰ cm⁻³.
 9. The insulating film according toclaim 7, wherein: the trivalent metal amount in the oxide dielectricfilm is equal to or larger than the hydrogen amount; and the trivalentmetal is located adjacent to each hydrogen atom.
 10. An insulating filmcomprising an amorphous oxide dielectric film containing a quadrivalentmetal, a divalent metal, and hydrogen, the divalent metal amount [IImetal] and the hydrogen amount [H] in the oxide dielectric filmsatisfying the following relationship:{2×[II metal]−[H]}/2≦1.0×10²¹ cm⁻³.
 11. The insulating film according toclaim 10, wherein the divalent metal amount [II metal] and the hydrogenamount [H] in the oxide dielectric film satisfy the followingrelationship:{2×[II metal]−[H]}/2≦3.0×10²⁰ cm⁻³.
 12. The insulating film according toclaim 10, wherein: the hydrogen amount in the oxide dielectric film isequal to or smaller than twice the divalent metal amount; and atoms ofthe divalent metal are located adjacent to the respective hydrogenatoms.
 13. An insulating film comprising an amorphous oxide dielectricfilm containing a trivalent metal, a divalent metal, and hydrogen, thedivalent metal amount [II metal] and the hydrogen amount [H] in theoxide dielectric film satisfying the following relationship:{[II metal]−[H]}/2≦1.0×10²¹ cm⁻³.
 14. The insulating film according toclaim 13, wherein the divalent metal amount [II metal] and the hydrogenamount [H] in the oxide dielectric film satisfy the followingrelationship:{[II metal]−[H]}/2≦3.0×10²⁰ cm⁻³.
 15. The insulating film according toclaim 13, wherein: the divalent metal amount in the oxide dielectricfilm is equal to or larger than the hydrogen amount; and atoms of thedivalent metal are located adjacent to the respective hydrogen atoms.16. A semiconductor device comprising: a semiconductor substrate; asource region and a drain region provided at a distance from each otherin the semiconductor substrate; the insulating film according to claim1, provided on a portion of the semiconductor substrate, the portionbeing a channel region between the source region and the drain region;and a gate electrode provided on the insulating film.
 17. Asemiconductor device comprising: a first electrode; the insulating filmaccording to claim 1, provided on the first electrode; and a secondelectrode provided on the insulating film.
 18. A semiconductor devicecomprising: a semiconductor substrate; a source region and a drainregion provided at a distance from each other in the semiconductorsubstrate; a first insulating film provided on a portion of thesemiconductor substrate, the portion being a channel region between thesource region and the drain region; a first electrode provided on thefirst insulating film; a second insulating film provided on the firstelectrode; and a second electrode provided on the second insulatingfilm, at least one of the first insulating film and the secondinsulating film being the insulating film according to claim
 1. 19. Asemiconductor device comprising: a semiconductor substrate; a sourceregion and a drain region provided at a distance from each other in thesemiconductor substrate; a first insulating film provided on a portionof the semiconductor substrate, the portion being a channel regionbetween the source region and the drain region; a charge trapping filmprovided on the first insulating film; a second insulating film providedon the charge trapping film; and an electrode provided on the secondinsulating film, at least one of the first insulating film, the chargetrapping film, and the second insulating film being the insulating filmaccording to claim 1.